XHTML™ 2.0

W3C Working Draft 6 May 2003

This version:

http://www.w3.org/TR/2003/WD-xhtml2-20030506

Latest version:

http://www.w3.org/TR/xhtml2

Previous version:

http://www.w3.org/TR/2003/WD-xhtml2-20030131

Diff-marked version:

xhtml2-diff.html

Editors:

Jonny Axelsson, Opera Software

Beth Epperson , Netscape/ AOL

Masayasu Ishikawa ,W3C

Shane McCarron , Applied Testing and Technology

Ann Navarro, WebGeek, Inc.

Steven Pemberton , CWI ( HTML Working Group Chair)

This document is also available in these non-normative formats: Single XHTML file , PostScript version , PDF version , ZIP archive , and Gzip'd TAR archive .

Copyright ©2003 W3C ^® ( MIT , ERCIM , Keio ), All Rights Reserved. W3C liability , trademark , document use and software licensing rules apply.

Abstract

XHTML 2 is a general purpose markup language designed for representing documents for a wide range of purposes across the World Wide Web. To this end it does not attempt to be all things to all people, supplying every possible markup idiom, but to supply a generally useful set of elements.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C.

This document is the fifth public Working Draft of this specification. It should in no way be considered stable, and should not be normatively referenced for any purposes whatsoever. This version includes an early implementation of XHTML 2.0 in RELAX NG [ RELAXNG ], but does not include the implementations in DTD or XML Schema form. Those will be included in subsequent versions, once the content of this language stabilizes. This version also does not address the issues revolving around the use of [ XLINK ] by XHTML 2. Those issues are being worked independent of the evolution of this specification. Those issues should, of course, be resolved as quickly as possible, and the resolution will be reflected in a future draft. Finally, the working group has started to resolve many of the issues that have been submitted by the public. If your particular issue has not yet been addressed, please be patient - there are many issues, and some are more complex than others.

This document has been produced by the W3C HTML Working Group ( members only ) as part of the W3C HTML Activity . The goals of the HTML Working Group are discussed in the HTML Working Group charter .

Public discussion of XHTML takes place on www-html@w3.org ( archive ). To subscribe send an email to www-html-request@w3.org with the word subscribe in the subject line.

Please report errors in this document to www-html-editor@w3.org ( archive ).

At the time of publication, the Working Group believed there were no patent disclosures relevant to this specification. A current list of patent disclosures relevant to this specification may be found on the Working Group's patent disclosure page .

A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR.

Quick Table of Contents

List of Issues

Full Table of Contents

1. Introduction

This section is informative .

1.1. What is XHTML 2?

XHTML 2 is a general purpose markup language designed for representing documents for a wide range of purposes across the World Wide Web. To this end it does not attempt to be all things to all people, supplying every possible markup idiom, but to supply a generally useful set of elements, with the possibility of extension using the span and div elements in combination with stylesheets.

1.1.1. Backwards compatibility

Because earlier versions of HTML were special-purpose languages, it was necessary to ensure a level of backwards compatibility with new versions so that new documents would still be usable in older browsers. However, thanks to XML and stylesheets, such strict element-wise backwards compatibility is no longer necessary, since an XML-based browser, of which at the time of writing means more than 95% of browsers in use, can process new markup languages without having to be updated. Much of XHTML2 works already in existing browsers. Much, but not all: just as when forms and tables were added to HTML, and people had to wait for new version of browsers before being able to use the new facilities, some parts of XHTML2, such as XForms and XML Events, still require user agents that understand that functionality.

1.1.2. XHTML2 and Presentation

The original version of HTML was designed to represent the structure of a document, not its presentation. Even though presentation-oriented elements were later added to the language by browser manufacturers, HTML is at heart a document structuring language. XHTML2 takes HTML back to these roots, by removing all presentation elements, and subordinating all presentation to stylesheets. This gives greater flexibility, and more powerful presentation possibilities, since CSS can do more than the presentational elements of HTML ever did.

1.1.3. Design Aims

In designing XHTML, a number of design aims were kept in mind to help direct the design. These included:

• As generic XML as possible: if a facility exists in XML, try to use that rather than duplicating it.
• Less presentation, more structure: already mentioned above.
• More usability: try to make the language easy to write, and make the resulting documents easy to use.
• More accessibility: some call it 'designing for our future selves'; the design should be as inclusive as possible.
• Better internationalization: it is a World Wide Web.
• More device independence: new devices coming online, such as telephones, PDAs, tablets, televisions and so on mean that it is imperative to have a design that allows you to author once and render in different ways on different devices, rather than authoring new versions of the document for each type of device.
• Less scripting: achieving functionality through scripting is difficult for the author and restricts the type of user agent you can use to view the document. We have tried to identify current typical usage, and include those usages in markup.

1.2. What are the XHTML 2 Modules?

XHTML 2 is a member of the XHTML Family of markup languages. It is an XHTML Host Language as defined in XHTML Modularization. As such, it is made up of a set of XHTML Modules that together describe the elements and attributes of the language, and their content model. XHTML 2 updates many of the modules defined in XHTML Modularization 1.0 [ XHTMLMOD ], and includes the updated versions of all those modules and their semantics. XHTML 2 also uses modules from Ruby [ RUBY ], XML Events [ XMLEVENTS ], and XForms [ XFORMS ].

The modules defined in this specification are largely extensions of the modules defined in XHTML Modularization 1.0. This specification also defines the semantics of the modules it includes. So, that means that unlike earlier versions of XHTML that relied upon the semantics defined in HTML 4 [ HTML4 ], all of the semantics for XHTML 2 are defined either in this specification or in the specifications that it normatively references.

Even though the XHTML 2 modules are defined in this specification, they are available for use in other XHTML family markup languages. Over time, it is possible that the modules defined in this specification will migrate into the XHTML Modularization specification.

2. Terms and Definitions

This section is informative .

While some terms are defined in place, the following definitions are used throughout this document. Familiarity with the W3C XML 1.0 Recommendation [ XML ] is highly recommended.

abstract module

a unit of document type specification corresponding to a distinct type of content, corresponding to a markup construct reflecting this distinct type.

content model

the declared markup structure allowed within instances of an element type. XML 1.0 differentiates two types: elements containing only element content (no character data) and mixed content (elements that may contain character data optionally interspersed with child elements). The latter are characterized by a content specification beginning with the "#PCDATA" string (denoting character data).

deprecated

a feature marked as deprecated is in the process of being removed from this recommendation. Portable applications should not use features marked as deprecated.

document model

the effective structure and constraints of a given document type. The document model constitutes the abstract representation of the physical or semantic structures of a class of documents.

document type

a class of documents sharing a common abstract structure. The ISO 8879 [ SGML ] definition is as follows: "a class of documents having similar characteristics; for example, journal, article, technical manual, or memo. (4.102)"

document type definition (DTD)

a formal, machine-readable expression of the XML structure and syntax rules to which a document instance of a specific document type must conform; the schema type used in XML 1.0 to validate conformance of a document instance to its declared document type. The same markup model may be expressed by a variety of DTDs.

driver

a generally short file used to declare and instantiate the modules of a DTD. A good rule of thumb is that a DTD driver contains no markup declarations that comprise any part of the document model itself.

element

an instance of an element type.

element type

the definition of an element, that is, a container for a distinct semantic class of document content.

entity

an entity is a logical or physical storage unit containing document content. Entities may be composed of parseable XML markup or character data, or unparsed (i.e., non-XML, possibly non-textual) content. Entity content may be either defined entirely within the document entity ("internal entities") or external to the document entity ("external entities"). In parsed entities, the replacement text may include references to other entities.

entity reference

a mnemonic string used as a reference to the content of a declared entity (eg., "&amp;" for "&", "&lt;" for "<", "&copy;" for "©".)

generic identifier

the name identifying the element type of an element. Also, element type name.

hybrid document

A hybrid document is a document that uses more than one XML namespace. Hybrid documents may be defined as documents that contain elements or attributes from hybrid document types.

instantiate

to replace an entity reference with an instance of its declared content.

markup declaration

a syntactical construct within a DTD declaring an entity or defining a markup structure. Within XML DTDs, there are four specific types: entity declaration defines the binding between a mnemonic symbol and its replacement content; element declaration constrains which element types may occur as descendants within an element (see also content model); attribute definition list declaration defines the set of attributes for a given element type, and may also establish type constraints and default values; notation declaration defines the binding between a notation name and an external identifier referencing the format of an unparsed entity.

markup model

the markup vocabulary (i.e., the gamut of element and attribute names, notations, etc.) and grammar (i.e., the prescribed use of that vocabulary) as defined by a document type definition (i.e., a schema) The markup model is the concrete representation in markup syntax of the document model, and may be defined with varying levels of strict conformity. The same document model may be expressed by a variety of markup models.

module

an abstract unit within a document model expressed as a DTD fragment, used to consolidate markup declarations to increase the flexibility, modifiability, reuse and understanding of specific logical or semantic structures.

modularization

an implementation of a modularization model; the process of composing or de-composing a DTD by dividing its markup declarations into units or groups to support specific goals. Modules may or may not exist as separate file entities (i.e., the physical and logical structures of a DTD may mirror each other, but there is no such requirement).

modularization model

the abstract design of the document type definition (DTD) in support of the modularization goals, such as reuse, extensibility, expressiveness, ease of documentation, code size, consistency and intuitiveness of use. It is important to note that a modularization model is only orthogonally related to the document model it describes, so that two very different modularization models may describe the same document type.

parameter entity

an entity whose scope of use is within the document prolog (i.e., the external subset/DTD or internal subset). Parameter entities are disallowed within the document instance.

parent document type

A parent document type of a hybrid document is the document type of the root element.

tag

descriptive markup delimiting the start and end (including its generic identifier and any attributes) of an element.

3. Conformance Definition

This section is normative .

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [ RFC2119 ].

3.1. Document Conformance

3.1.1. Strictly Conforming Documents

A strictly conforming XHTML 2.0 document is a document that requires only the facilities described as mandatory in this specification. Such a document must meet all the following criteria:

1. The document must conform to the constraints expressed in Appendix B - XHTML 2.0 RELAX NG Definition ,Appendix D - XHTML 2.0 Schema or Appendix F - XHTML 2.0 Document Type Definition .

2. The root element of the document must be html .

3. The root element of the document must contain an xmlns declaration for the XHTML 2.0 namespace [ XMLNAMES ]. The namespace for XHTML 2.0 is defined to be http://www.w3.org/2002/06/xhtml2 . An example root element might look like:

   <html xmlns="http://www.w3.org/2002/06/xhtml2" xml:lang="en">
   

4. There must be a DOCTYPE declaration in the document prior to the root element. If present, the public identifier included in the DOCTYPE declaration must reference the DTD found in Appendix F using its Public Identifier. The system identifier may be modified appropriately.

   <!DOCTYPE
    html PUBLIC "-//W3C//DTD XHTML 2.0//EN"
    "TBD">
   

Here is an example of an XHTML 2.0 document.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 2.0//EN"
    "TBD">
<html xmlns="http://www.w3.org/2002/06/xhtml2" xml:lang="en">
  <head>
    <title>Virtual Library</title>
  </head>
  <body>
    <p>Moved to <a href="http://vlib.org/">vlib.org</a>.</p>
  </body>
</html>

Note that in this example, the XML declaration is included. An XML declaration like the one above is not required in all XML documents. XHTML document authors are strongly encouraged to use XML declarations in all their documents. Such a declaration is required when the character encoding of the document is other than the default UTF-8 or UTF-16 and no encoding was determined by a higher-level protocol.

3.2. User Agent Conformance

A conforming user agent must meet all user agent conformance requirements defined in [ XHTMLMOD ].

4. The XHTML 2.0 Document Type

This section is normative .

The XHTML 2.0 document type is a fully functional document type with rich semantics. It is a collection of XHTML-conforming modules (most of which are defined in this specification). The Modules and their elements are listed here for information purposes, but the definitions in their base documents should be considered authoritative. In the on-line version of this document, the module names in the list below link into the definitions of the modules within the relevant version of the authoritative specification.

Structure Module *

body, head, html, title

Block Text Module *

address, blockcode, blockquote, div, h, h1, h2, h3, h4, h5, h6, hr, p, pre, section

Inline Text Module *

abbr, cite, code, dfn, em, kbd, l, quote, samp, span, strong, sub, sup, var

Hypertext Module *

a

List Module *

dl, dt, dd, label, nl, ol, ul, li

Link Module

link

Metainformation Module

meta

Object Module

object, param, standby

Scripting Module

noscript, script

Style Attribute Module

style attribute

Stylesheet Module

style element

Tables Module

caption, col, colgroup, summary, table, tbody, td, tfoot, th, thead, tr

XHTML 2.0 also uses the following externally defined modules:

Ruby Annotation Module [ RUBY ]

ruby, rbc, rtc, rb, rt, rp

XML Events Module [ XMLEVENTS ]

listener

XForms Module [ XFORMS ]

action, alert, bind, case, choices, copy, delete, dispatch, extension, filename, group, help, hint, input, insert, instance, item, itemset, label, load, mediatype, message, model, output, range, rebuild, recalculate, refresh, repeat, reset, revalidate, secret, select, select1, send, setfocus, setindex, setvalue, submission, submit, switch, textarea, toggle, trigger, upload, value

There are no additional definitions required by this document type. An implementation of this document type as a RELAX NG grammar is defined in Appendix B ,as an XML Schema in Appendix D , and as a DTD in Appendix F .

5. Module Definition Conventions

This section is normative .

This document defines a variety of XHTML modules and the semantics of those modules. This section describes the conventions used in those module definitions.

5.1. Module Structure

Each module in this document is structured in the following way:

• An abstract definition of the module's elements, attributes, and content models, as appropriate.
• A sub-section for each element in the module; These sub-sections contain the following components:
  • A brief description of the element,
  • A definition of each attribute or attribute collection usable with the element, and
  • A detailed description of the behavior of the element, if appropriate.

  Note that attributes are fully defined only the first time they are used in each module. After that, only a brief description of the attribute is provided, along with a link back to the primary definition.

5.2. Abstract Module Definitions

An abstract module is a definition of an XHTML module using prose text and some informal markup conventions. While such a definition is not generally useful in the machine processing of document types, it is critical in helping people understand what is contained in a module. This section defines the way in which XHTML abstract modules are defined. An XHTML-conforming module is not required to provide an abstract module definition. However, anyone developing an XHTML module is encouraged to provide an abstraction to ease in the use of that module.

5.3. Syntactic Conventions

The abstract modules are not defined in a formal grammar. However, the definitions do adhere to the following syntactic conventions. These conventions are similar to those of XML DTDs, and should be familiar to XML DTD authors. Each discrete syntactic element can be combined with others to make more complex expressions that conform to the algebra defined here.

element name

When an element is included in a content model, its explicit name will be listed.

content set

Some modules define lists of explicit element names called content sets . When a content set is included in a content model, its name will be listed.

expr ?

Zero or one instances of expr are permitted.

expr +

One or more instances of expr are required.

expr *

Zero or more instances of expr are permitted.

a , b

Expression a is required, followed by expression b .

a | b

Either expression a or expression b is required.

a - b

Expression a is permitted, omitting elements in expression b.

parentheses

When an expression is contained within parentheses, evaluation of any subexpressions within the parentheses take place before evaluation of expressions outside of the parentheses (starting at the deepest level of nesting first).

extending pre-defined elements

In some instances, a module adds attributes to an element. In these instances, the element name is followed by an ampersand ( & ).

defining required attributes

When an element requires the definition of an attribute, that attribute name is followed by an asterisk ( * ).

defining the type of attribute values

When a module defines the type of an attribute value, it does so by listing the type in parentheses after the attribute name.

defining the legal values of attributes

When a module defines the legal values for an attribute, it does so by listing the explicit legal values (enclosed in quotation marks), separated by vertical bars ( | ), inside of parentheses following the attribute name. If the attribute has a default value, that value is followed by an asterisk ( * ). If the attribute has a fixed value, the attribute name is followed by an equals sign ( = ) and the fixed value enclosed in quotation marks.

5.4. Content Types

Abstract module definitions define minimal, atomic content models for each module. These minimal content models reference the elements in the module itself. They may also reference elements in other modules upon which the abstract module depends. Finally, the content model in many cases requires that text be permitted as content to one or more elements. In these cases, the symbol used for text is PCDATA . This is a term, defined in the XML 1.0 Recommendation, that refers to processed character data. A content type can also be defined as EMPTY , meaning the element has no content in its minimal content model.

5.5. Attribute Types

In some instances, it is necessary to define the types of attribute values or the explicit set of permitted values for attributes. The following attribute types (defined in the XML 1.0 Recommendation) are used in the definitions of the abstract modules:

In addition to these pre-defined data types, XHTML Modularization defines the following data types and their semantics (as appropriate):

6. XHTML Attribute Collections

This section is normative .

Many of the abstract modules in this document define the required attributes for their elements. The table below defines some collections of attributes that are referenced throughout the modules. These expressions should in no way be considered normative or mandatory. They are an editorial convenience for this document. When used in the remainder of this section, it is the expansion of the term that is normative, not the term itself.

The following basic attribute sets are used on many elements. In each case where they are used, their use is identified via their collection name.

6.1. Core Attribute Collection

class = NMTOKENS

This attribute assigns one or more class names to an element; the element may be said to belong to these classes. A class name may be shared by several element instances.

The class attribute can be used for different purposes in XHTML, for instance as a style sheet selector (when an author wishes to assign style information to a set of elements), and for general purpose processing by user agents.

For instance in the following example, the p element is used in conjunction with the class attribute to identify a particular type of paragraph.

<p class="note">
These programs are only available if you have purchased
the advanced professional suite.
</p>

Style sheet rules can then be used to render the paragraph appropriately, for instance by putting a border around it, giving it a different background colour, or where necessary by not displaying it at all.

id = ID

The id attribute assigns an identifier to an element. The id of an element must be unique within a document.

The id attribute has several roles in XHTML:

• As a style sheet selector.
• As a target anchor for hypertext links.
• As a means to reference a particular element from a script .
• As the name of a declared object element.
• For general purpose processing by user agents (e.g. for identifying fields when extracting data from XHTML pages into a database, translating XHTML documents into other formats, etc.).

As an example, the following headings are distinguished by their id values:

<h id="introduction">Introduction</h>
<p>...</p>
<h id="events">The Events Module</h>
<p>...</p>

title = Text

This attribute offers advisory information about the element for which it is set.

Values of the title attribute may be used by user agents in a variety of ways. For instance, visual browsers should display the title as a "tool tip" (a short message that appears when the pointing device pauses over an object). Audio user agents may speak the title information in a similar context.

Example of the use of title :

<a href="/Jakob/" title="Author biography">Jakob Nielsen</a>'s
Alertbox for January 11, 1998

The title attribute has an additional role when used with the link element to designate an external style sheet. See the section on links and style sheets for details.

6.2. I18N Attribute Collection

xml:lang = LanguageCode

This attribute specifies the base language of an element's attribute values and text content. It is defined normatively in [ XML ] section 2.12 . The default value of this attribute is unspecified.

An element inherits language code information according to the following order of precedence (highest to lowest):

• The xml:lang attribute set for the element itself.
• The closest parent element that has the xml:lang attribute set (i.e., the xml:lang attribute is inherited).
• The HTTP "Content-Language" header (which may be configured in a server).

In this example, the primary language of the document is French ("fr"). One paragraph is declared to be in US English ("en-us"), after which the primary language returns to French. The following paragraph includes an embedded Japanese ("ja") phrase, after which the primary language returns to French.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 2.0//EN"
   "TBD">
<html xmlns="http://www.w3.org/2002/06/xhtml2" xml:lang="fr">
<head>
   <title>Un document multilingue</title>
</head>
<body>
<p>...Interpreted as French...</p>
<p xml:lang="en-us">...Interpreted as US English...</p>
<p>...Interpreted as French again...</p>
<p>...French text interrupted by<em xml:lang="ja">some
         Japanese</em>French begins here again...</p>
</body>
</html>

6.3. Bi-directional Text Collection

dir = "ltr|rtl|lro|rlo"

This attribute specifies the base direction of the element's text content. This direction overrides the inherent directionality of characters as defined in [ UAX9 ], and defines directional properties of text as defined by CSS2 [ CSS2 ]. The default value of this attribute is user-agent dependent. Possible values are:

• ltr : Left-to-right text. The effect of this attribute is defined by the CSS2 rule:

  *[dir="ltr"] { unicode-bidi: embed; direction: ltr}
  
  

• rtl : Right-to-left text. The effect of this attribute is defined by the CSS2 rule:

  *[dir="rtl"] { unicode-bidi: embed; direction: rtl}
  
  

• lro : Left-to-right override. The effect of this attribute is defined by the CSS2 rule:

  *[dir="lro"] { unicode-bidi: bidi-override; direction: ltr}
  

• rlo : Right-to-left override. The effect of this attribute is defined by the CSS2 rule:

  *[dir="rlo"] { unicode-bidi: bidi-override; direction: rtl}
  

Example:

improve bidi example

This example is sort of contrived. Can't we come up with a real-world example that is actually interesting?

<p dir="ltr">
I received the following email:
<l dir="lro">english werbeh english</l>
<l dir="lro">werbeh english werbeh</l>
</p>

6.3.1. Inheritance of text direction information

The Unicode bidirectional algorithm requires a base text direction for text blocks. To specify the base direction of a block-level element, set the element's dir attribute. The default value of the dir attribute is "ltr" (left-to-right text).

When the dir attribute is set for a block-level element, it remains in effect for the duration of the element and any nested block-level elements. Setting the dir attribute on a nested element overrides the inherited value.

To set the base text direction for an entire document, set the dir attribute on the html element.

Example:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 2.0//EN"
   "http://www.w3.org/TR/xhtml2/DTD/xhtml2.dtd">
<html dir="rtl">
<head>
<title>...a right-to-left title...</title>
</head>
...right-to-left text...<p dir="ltr">...left-to-right text...</p>
<p>...right-to-left text again...</p>
</html>

Inline elements, on the other hand, do not inherit the dir attribute. This means that an inline element without a dir attribute does not open an additional level of embedding with respect to the bidirectional algorithm. (Here, an element is considered to be block-level or inline based on its default presentation.)

6.3.2. The effect of style sheets on bidirectionality

In general, using style sheets to change an element's visual rendering from block-level to inline or vice-versa is straightforward. However, because the bidirectional algorithm relies on the inline/block-level distinction, special care must be taken during the transformation.

When an inline element that does not have a dir attribute is transformed to the style of a block-level element by a style sheet, it inherits the dir attribute from its closest parent block element to define the base direction of the block.

When a block element that does not have a dir attribute is transformed to the style of an inline element by a style sheet, the resulting presentation should be equivalent, in terms of bidirectional formatting, to the formatting obtained by explicitly adding a dir attribute (assigned the inherited value) to the transformed element.

6.4. Edit Collection

This collection allows elements to carry information indicating how, when and why content has changed.

edit = "inserted|deleted|changed|moved"

This attribute allows elements to carry information indicating how content has changed. Possible values:

• inserted : the content has been inserted
• deleted : the content has been deleted
• changed : the content has changed considerably, therefore making it not worth being marked up with values of inserted and deleted
• moved : the content has been moved from some other part of the document.

The default presentation for an element with edit="deleted" is display: none (in other words, it is not displayed) although an alternate style might display it as crossed through. The other three values cause no special presentation by default, though an alternate style might use background colors or other text decoration to indicate the changed text.

Example:

<p>I will do it
next <span edit="deleted">week</span><span edit="inserted">month</span>.</p>

datetime = Datetime

The value of this attribute specifies the date and time when a change was made.

Example:

datetime="2003-01-13T13:15:30Z"

6.5. Hypertext Attribute Collection

This collection allows an element to be the start point of a hypertext link to a remote resource.

href = URI

This attribute specifies a URI that is actuated when the element is activated.

Examples:

<abbr href="http://www.w3.org/" title="World Wide Web">WWW</abbr>
<li href="contents.xhtml">contents</li>
<a href="http://www.cwi.nl/~steven/amsterdam.html">Amsterdam</a>
<quote href="hamlet.xhtml#p2435">To be or not to be</quote>
<var href="#index_ninc">ninc</var>

cite = URI

The value of this attribute is a URI that designates a source document or message. This attribute is intended to give further information about the element's contents (e.g., the source from which a quotation was borrowed, or the reason text was inserted or deleted). User Agents should provide a means for the user to access the further information.

Example:

cite="comments.html"

target = HrefTarget

This attribute identifies an environment that will act as the destination for a resource identified by a hyperlink when it is activated.

This specification does not define how this attribute gets used, since that is defined by the environment that the hyperlink is actuated in. See for instance XFrames [ XFRAMES ].

Example:

<a href="home.html" target="main">Home</a>

rel = LinkTypes

This attribute describes the relationship from the current document to the URI referred to by the element. The value of this attribute is a space-separated list of link types.

Example:

<link href="top.html" rel="contents"/>

rev = LinkTypes

This attribute is used to describe a reverse link from the anchor specified by the href attribute to the current document. The value of this attribute is a space-separated list of link types.

accesskey = Character

This attribute assigns an access key to an element. An access key is a single character from the document character set. Note. Authors should consider the input method of the expected reader when specifying an accesskey.

Pressing an access key assigned to an element gives focus to the element. The action that occurs when an element receives focus depends on the element. For example, when a user activates a link defined by the a element, the user agent generally follows the link. When a user activates a radio button, the user agent changes the value of the radio button. When the user activates a text field, it allows input, etc.

In this example, we assign the access key "C" to a link. Typing this access key takes the user to another document, in this case, a table of contents.

<p accesskey="C" 
   rel="contents"
   href="http://example.com/specification/contents.html">
  Table of Contents
</p>

The invocation of access keys depends on the underlying system. For instance, on machines running MS Windows, one generally has to press the "alt" key in addition to the access key. On Apple systems, one generally has to press the "cmd" key in addition to the access key.

The rendering of access keys depends on the user agent. We recommend that authors include the access key in label text or wherever the access key is to apply. User agents should render the value of an access key in such a way as to emphasize its role and to distinguish it from other characters (e.g., by underlining it).

Accesskey

Actuation of elements with accesskey

navindex = Number

This attribute specifies the position of the current element in the navigation order for the current document. This value must be a number between 0 and 32767. User agents must ignore leading zeros.

The navigation order defines the order in which elements will receive focus when navigated by the user via the keyboard. The navigation order may include elements nested within other elements.

Elements that may receive focus should be navigated by user agents according to the following rules:

1. Those elements that support the navindex attribute and assign a positive value to it are navigated first. Navigation proceeds from the element with the lowest navindex value to the element with the highest value. Values need not be sequential nor need they begin with any particular value. Elements that have identical navindex values should be navigated in the order they appear in the character stream.
2. Those elements that do not support the navindex attribute or support it and assign it a value of "0" are navigated next. These elements are navigated in the order they appear in the character stream.

When a document is loaded using a URL that includes a fragment reference (such as book.html#chapter5 ) navigation begins at the point the fragment begins. If the user has moved away from that point (for instance using page up or page down), the navigation starting point is undefined.

The following example would allow the links to be navigated in column order (without the use of navindex they would be navigated in document, i.e. row, order):

<table>
<tr><td href="a" navindex="1">NW</td>
    <td href="c" navindex="3">NE</td></tr>
<tr><td href="b" navindex="2">SW</td>
    <td href="d" navindex="4">SE</td></tr>
</table>

Navigation keys. The actual key sequence that causes navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key might be used for navigation and the "enter" key or "space" key used to activate a selected element).

User agents may also define key sequences to navigate the navigation order in reverse. When the end (or beginning) of the navigation order is reached, user agents may circle back to the beginning (or end).

xml:base = URI

This attribute specifies the base URI from which to resolve relative URIs. It is normatively defined in [ XMLBASE ]. Any relative URI used on an element that uses this attribute, or on an element contained within an element that uses this attribute, must be resolved relative to the base URI defined by this attribute.

An element inherits URI base information according to the following order of precedence (highest to lowest):

• The xml:base attribute set for the element itself.
• The closest parent element that has the xml:base attribute set (i.e., the xml:base attribute is inherited).
• The HTTP "Content-Location" header (which may be configured in a server).
• The location of the document itself.

Example:

See:
<ul xml:base="http://www.w3.org">
<li href="/">The W3C home page</li>
<li href="/TR">The W3C Technical Reports page</li>
<li href="/Markup">The HTML home page</li>
<li href="/Markup/Forms">The XForms home page</li>
</ul>

6.6. Embedding Attribute Collection

This collection causes the contents of a remote resource to be embedded in the document in place of the element's content. If accessing the remote resource fails, for whatever reason (network unavailable, no resource available at the URI given, inability of the user agent to process the type of resource) the content of the element must be processed instead.

Note that this behavior makes documents far more robust, and gives much better opportunities for accessible documents than the longdesc attribute present in earlier versions of XHTML, since it allows the description of the resource to be included in the document itself, rather than in a separate document.

Examples:

<p src="holiday.png" type="image/png">
    <span src="holiday.gif" type="image/gif">
        An image of us on holiday.
    </span>
</p>
<table src="temperature-graph.png" type="image/png">
<caption>Average monthly temperature over the last 20 years</caption>
<tr><th>Jan</th><th>Feb</th><th>Mar</th><th>Apr</th><th>May</th><th>Jun</th>
    <th>Jul</th><th>Aug</th><th>Sep</th><th>Oct</th><th>Nov</th><th>Dec</th>
</tr>
<tr><td> 4</td><td> 2</td><td> 7</td><td> 9</td><td>13</td><td>16</td>
    <td>17</td><td>17</td><td>14</td><td>11</td><td> 7</td><td> 4</td>
</tr>
</table>

src = URI

This attribute specifies the location of an external source for the contents of the element.

type = ContentType

This attribute specifies the allowable content types of the relevant src URI. At its most general, it is a comma-separated list of media ranges with optional accept parameters, as defined in section 14.1 of [ RFC2616 ] as the field value of the accept request header.

In its simplest case, this is just a media type, such as "image/png" or "application/xml", but it may also contain asterisks, such as "image/*" or "*/*", or lists of acceptable media types, such as "image/png, image/gif, image/jpeg".

The user agent must combine this list it with its own list of acceptable media types by taking the intersection, and then use the resulting list as the field value of the accept request header when requesting the resource using HTTP.

For instance, if the attribute specifies the value "image/png, image/gif, image/jpeg", but the user agent does not accept images of type "image/gif" then the resultant accept header would contain "image/png, image/jpeg".

A user agent should imitate similar behavior when using other methods than HTTP. For instance, when accessing files in a local filestore, <p src="logo" type="image/png, image/jpeg"> might cause the user agent first to look for a file logo.png , and then for logo.jpg .

If this attribute is not present, "*/*" is used for its value.

For the current list of registered content types, please consult [ MIMETYPES ].

Examples:

<script src="pop" type="application/x-javascript, text/x-newspeak"/>
<style src="midnight" type="text/css, text/x-mystyle"/>
<p src="w3c-logo" type="image/png, image/jpeg;q=0.2">W3C logo</p>
<span src="logo.png">Our logo</span>
<span src="theme.mp3" type="audio/x-mpeg">Our theme jingle</span>

6.7. Image Map Attribute Collection

This collection adds attributes that specify that an embedded image may be used as an image map, so that clicking on different parts of the image causes different hyperlinks to be activated.

usemap = URI

This attribute associates an image map with an element. The value of usemap must match the value of the id attribute of an element that contains one or more elements with shape and coords attributes.

ismap = "ismap"

This attribute indicates that the associated image is to be treated as a "server-side image map". When selected, the coordinates within the element that the user selected are sent to the server where the document resides. Screen coordinates are expressed as screen pixel values relative to the image, and start at (0,0) at the top left corner.

In the following example, the active region defines a server-side image map. A click anywhere on the image will cause the click's coordinates to be sent to the server.

<p href="http://www.example.com/cgi-bin/map"
      src="map.png" ismap="ismap">
   Our location.
</p>

The location clicked is passed to the server as follows. The user agent derives a new URI from the URI specified by the href attribute of the element, by appending `?' followed by the x and y coordinates, separated by a comma. The link is then actuated using the new URI. For instance, in the given example, if the user clicks at the location x=10, y=27 then the derived URI is "http://www.example.com/cgi-bin/map?10,27".

User agents that do not offer the user a means to select specific coordinates (e.g., non-graphical user agents that rely on keyboard input, speech-based user agents, etc.) should send the coordinates "0,0" to the server when the link is activated.

shape = "default|rect|circle|poly"

This attribute specifies the shape of a region. Possible values:

• default: Specifies the entire region.
• rect: Define a rectangular region.
• circle: Define a circular region.
• poly: Define a polygonal region.

coords = Coordinates

This attribute specifies the position and shape of the area. The number and order of values depends on the shape being defined. Possible combinations:

• rect: left-x, top-y, right-x, bottom-y.
• circle: center-x, center-y, radius. Note. When the radius value is a percentage value, user agents should calculate the final radius value based on the associated object's width and height. The radius should be the smaller value of the two.
• poly: x1, y1, x2, y2, ..., xN, yN. The first x and y coordinate pair and the last should be the same to close the polygon. When these coordinate values are not the same, user agents should infer an additional coordinate pair to close the polygon.

Coordinates are relative to the top, left corner of the object. All values are of type Length . All values are separated by commas. The coordinates of the top, left corner of an area are 0, 0 .

Note that in the following example, if the image is unavailable for any reason, the fallback properties of the src attribute mean that the <nl> will be displayed instead of the image, thus making the page still useful:

 
<html xmlns="http://www.w3.org/2002/06/xhtml2">
   <head>
      <title>The cool site!</title>
   </head> 
   <body>
     <p src="navbar1.png" type="image/png" usemap="#map1"> 
         <nl id="map1">
           <label>Navigate the site:</label>
           <li href="guide.html" shape="rect" coords="0,0,118,28">
           Access Guide</li> 
           <li href="shortcut.html" shape="rect" coords="118,0,184,28">
           Go</li> 
           <li href="search.html" shape="circle" coords="184,200,60">
           Search</li>
           <li href="top10.html" shape="poly" coords="276,0,276,28,100,200,50,50,276,0">
           Top Ten</li>
         </nl>
      </p>
   </body>
</html> 

Note that an li in an nl is not required to have an href attribute. In that case, the relevant region of the image is inactive:

<p src="image.png" type="image/png" usemap="#map1">
   <nl id="map1">
   <li shape="circle" coords="100,200,50">I'm inactive.</li>
   <li href="outer-ring-link.html" shape="circle" coords="100,200,250">I'm active.</li>
   </nl>
</p>

6.8. Events

The global attributes from [ XMLEVENTS ] are included in the Events attribute collection. The normative definition of those attributes and their semantics is included in that specification. They are described briefly below:

defaultAction = cancel|perform

This attribute defines whether or not the default action associated with the event should be processed. The default value is perform

event = CDATA

This attribute defines the event type that is being listened for. The set of legal names for XHTML 2 is to be defined.

List of XHTML 2 Events Needed

We need to define the list of XHTML 2 events and map them into the XHTML DOM. activate, load, focusIn, focusOut, ...

handler = IDREF

This attribute specifies the ID of a handler element that defines the action that should be performed if the event reaches the observer.

observer = IDREF

This attribute specifies an ID for an observer element for which the listener is to be registered.

phase = capture|default

This attribute specifies the phase of event propagation in which to process the event. If not specified, the default value of this attribute is default .

propagate = stop|continue

This attribute specifies whether an event should stop propagating after this observer processes it, or continue for possible further processing. The default value of this attribute is continue .

target = IDREF

This attribute specifies the id of the target element of the event (i.e., the node that caused the event). If not specified, the default value of this attribute is the element on which the event attribute is specified.

Note that these attributes are not in the XHTML namespace but in the XML Events namespace. The XHTML namespace is the default namespace for XHTML documents, so XHTML elements and attributes may be expressed without namespace prefixes (although they are permitted on elements). XML Events attributes MUST use a prefix, since they are not in the default namespace of the document.

6.9. Style Attribute Collection

style = CDATA

This attribute specifies style information for the current element.

The syntax of the value of the style attribute is determined by the default style sheet language. For example, for [ CSS2 ] inline style, use the declaration block syntax described in the Style Sheet Module (without curly brace delimiters).

This CSS example sets color and font size information for the text in a specific paragraph.

<p style="font-size: 12pt; color: fuchsia">Aren't style sheets wonderful?</p>

In CSS, property declarations have the form "name : value" and are separated by a semi-colon.

To specify style information for more than one element, authors should use the style element. For optimal flexibility, authors should define styles in external style sheets.

Style Attributes and Generic XML

There is currently no way to declare what attribute within a given namespace contains "styling" information in a way that a Generic XML processor can discern. In an ideal world, someone would define such a mechanism (e.g., through the xml-stylesheet PI).

Note that the Style collection is only defined when the Style Attribute Module is selected. Otherwise, the Style collection is empty.

6.10. Common Attribute Collection

This collection assembles the Core , I18N , Events , Edit , Embedding , Map ,Style , Bi-directional , and Hypertext attribute collections defined above.

7. XHTML Structure Module

This section is normative .

The Structure Module defines the major structural elements for XHTML. These elements effectively act as the basis for the content model of many XHTML family document types. The elements and attributes included in this module are:

This module is the basic structural definition for XHTML content. The html element acts as the root element for all XHTML Family Document Types.

Note that the value of the xmlns attribute is defined to be "http://www.w3.org/2002/06/xhtml2". Also note that because the xmlns attribute is treated specially by XML namespace-aware parsers [ XMLNAMES ], it is legal to have it present as an attribute of each element. However, any time the xmlns attribute is used in the context of an XHTML module, whether with a prefix or not, the value of the attribute shall be the XHTML namespace defined here.

Implementation: RELAX NG

7.1. The html element

After the document type declaration, the remainder of an XHTML document is contained by the html element.

Example:

<html class="slideshow">

7.2. The head element

The head element contains information about the current document, such as its title, keywords that may be useful to search engines, and other data that is not considered document content. The default presentation of the head is not to display it; however that can be overridden with a stylesheet for special purpose use. User agents may however make information in the head available to users through other mechanisms.

Example:

<head>
    <title>My Life</title>
</head>

7.3. The title element

Every XHTML document must have a title element in the head section.

The title element is used to identify the document. Since documents are often consulted out of context, authors should provide context-rich titles. Thus, instead of a title such as "Introduction", which doesn't provide much contextual background, authors should supply a title such as "Introduction to Medieval Bee-Keeping" instead.

For reasons of accessibility, user agents must always make the content of the title element available to users. The mechanism for doing so depends on the user agent (e.g., as a caption, spoken).

Example:

<title>A study of population dynamics</title>

7.4. The body element

The body of a document contains the document's content. The content may be presented by a user agent in a variety of ways. For example, for visual browsers, you can think of the body as a canvas where the content appears: text, images, colors, graphics, etc. For audio user agents, the same content may be spoken.

8. XHTML Block Text Module

This section is normative .

This module defines all of the basic text container elements, attributes, and their content models that are "block level". Note that while the concept of "block level" can be construed as a presentation aspect, in this case it is intended to only have a semantic meaning.

The minimal content model for this module defines some content sets:

Heading

h | h1 | h2 | h3 | h4 | h5 | h6

Block

address | blockcode | blockquote | div | p | pre | section

Flow

Heading | Block | Inline

Note that the use of the words Block and Inline here are meant to be suggestive of the role the content sets play. They are not normative with regards to presentation since a style sheet might give any element within the Block content a display property of inline .

Implementation: RELAX NG

8.1. The address element

The address element may be used by authors to supply contact information for a document or a major part of a document such as a form. This element often appears at the beginning or end of a document.

<address href="mailto:webmaster@example.net">Webmaster</address>

8.2. The blockcode element

This element indicates that its contents are a block of "code" (see the code element). This element is similar to the pre element, in that whitespace in the enclosed text has semantic relevance. The whitespace should normally be included in visual renderings of the content.

Non-visual user agents are not required to respect extra white space in the content of a blockcode element.

<blockcode class="Perl">
sub squareFn {
    my $var = shift;
    return $var * $var ;
}
</blockcode>

sub squareFn {    my $var = shift;
    return $var * $var ;
}

8.3. The blockquote element

This element designates a block of quoted text.

<blockquote cite="http://www.example.com/tolkien/twotowers.html">
<p>They went in single file, running like hounds on a strong scent,
and an eager light was in their eyes. Nearly due west the broad
swath of the marching Orcs tramped its ugly slot; the sweet grass
of Rohan had been bruised and blackened as they passed.</p>
</blockquote>

8.4. The div element

The div element, in conjunction with the id and class attributes, offers a generic mechanism for adding extra structure to documents. This element defines no presentational idioms on the content. Thus, authors may use this element in conjunction with style sheets , the xml:lang attribute, etc., to tailor XHTML to their own needs and tastes.

<body>
    <h>The meaning of life</h>
    <p>By Huntington B. Snark</p>
    <div class="slide">
        <h>What do I mean by "life"</h>
        <p>....</p>
    </div>
    <div class="slide">
        <h>What do I mean by "mean"?</h>
        ...
    </div>
    ...
</body>

8.5. The heading elements

A heading element briefly describes the topic of the section it introduces. Heading information may be used by user agents, for example, to construct a table of contents for a document automatically.

There are two styles of headings in XHTML: the numbered versions h1 , h2 etc., and the structured version h , which is used in combination with the section element.

There are six levels of numbered headings in XHTML with h1 as the most important and h6 as the least. The visual presentation of headers can render more important headings in larger fonts than less important ones.

Structured headings use the single h element, in combination with the section element to indicate the structure of the document, and the nesting of the sections indicates the importance of the heading. The heading for the section is the one that is a child of the section element.

<body>
<h>This is a top level heading</h>
<p>....</p>
<section>
    <p>....</p>
    <h>This is a second-level heading</h>
    <p>....</p>
    <h>This is another second-level heading</h>
    <p>....</p>
</section>
<section>
    <p>....</p>
    <h>This is another second-level heading</h>
    <p>....</p>
    <section>
        <h>This is a third-level heading</h>
        <p>....</p>
    </section>
</section>

h {font-family: sans-serif; font-weight: bold; font-size: 200%}
section h {font-size: 150%} /* A second-level heading */
section section h {font-size: 120%} /* A third-level heading */

8.6. The hr element

The hr element places a horizontal line in the document.

8.7. The p element

The p element represents a paragraph.

In comparison with earlier versions of HTML, where a paragraph could only contain inline text, XHTML2's paragraphs represent the conceptual idea of a paragraph, and so may contain lists, blockquotes, pre's and tables as well as inline text. They may not, however, contain directly nested p elements.

<p>Payment options include:
<ul>
<li>cash</li>
<li>credit card</li>
<li>luncheon vouchers.</li>
</ul>
</p>

8.8. The pre element

The pre element indicates that whitespace in the enclosed text has semantic relevance, and will normally be included in visual renderings of the content.

Note that all elements in the XHTML family preserve their whitespace in the document, which is only removed on rendering, via a stylesheet, according to the rules of CSS [CSS]. This means that in principle any elements may preserve or collapse whitespace on rendering, under control of a stylesheet. Also note that there is no normative requirement that the <pre> element be rendered in a monospace font (although this is the default rendering), nor that text wrapping be disabled.

Non-visual user agents are not required to respect extra white space in the content of a pre element.

<pre>
       Higher still and higher
         From the earth thou springest
       Like a cloud of fire;
         The blue deep thou wingest,
And singing still dost soar, and soaring ever singest.
</pre>

       Higher still and higher
         From the earth thou springest
       Like a cloud of fire;
         The blue deep thou wingest,
And singing still dost soar, and soaring ever singest.

8.9. The section element

The section element, in conjunction with the h element, offers a mechanism for structuring documents into sections. This element defines content to be block-level but imposes no other presentational idioms on the content, which may otherwise be controlled from a style sheet.

<body>
<h>Events</h>
<section>
    <h>Introduction</h>
    <p>....</p>
    <h>Specifying events</h>
    <p>...</p>
    <section>
        <h>Attaching events to the handler</h>
        <p>...</p>
    </section>
    <section>
        <h>Attaching events to the listener</h>
        <p>...</p>
    </section>
    <section>
        <h>Specifying the binding elsewhere</h>
        <p>...</p>
    </section>
</section>    

9. XHTML Inline Text Module

This section is normative .

This module defines all of the basic text container elements, attributes, and their content models that are "inline level". Note that while the concept of "inline level" can be construed as a presentation aspect, in this case it is intended to only have a semantic meaning.

The minimal content model for this module defines a content set:

Inline

abbr | cite | code | dfn | em | kbd | l | quote | samp | span | strong | var

Note that the use of the words Block and Inline here are meant to be suggestive of the role the content sets play. They are not normative with regards to presentation since a style sheet might give any element within the Block content a display property of inline .

Implementation: RELAX NG

9.1. The abbr element

The abbr element indicates that a text fragment is an abbreviation (e.g., W3C, XML, Inc., Ltd., Mass., etc.); this includes acronyms.

The content of the abbr element specifies the abbreviated expression itself, as it would normally appear in running text. The title attribute of these elements may be used to provide the full or expanded form of the expression.

Note that abbreviations often have idiosyncratic pronunciations. For example, while "IRS" and "BBC" are typically pronounced letter by letter, "NATO" and "UNESCO" are pronounced phonetically. Still other abbreviated forms (e.g., "URI" and "SQL") are spelled out by some people and pronounced as words by other people. When necessary, authors should use style sheets to specify the pronunciation of an abbreviated form.

  <abbr title="Limited">Ltd.</abbr>
  <abbr title="Abbreviation">abbr.</abbr>

9.2. The cite element

The cite element contains a citation or a reference to other sources.

In the following example, the cite element is used to delineate the speaker:

As <cite cite="http://www.whitehouse.gov/history/presidents/ht33.html">Harry S. Truman</cite> said,
<quote xml:lang="en-us">The buck stops here.</quote>
More information can be found in <cite cite="http://www.w3.org/TR/REC-xml">[XML]</cite>.

9.3. The code element

The code element contains a fragment of computer code.

The Pascal statement <code>i := 1;</code> assigns the
literal value one to the variable <var>i</var>.

9.4. The dfn element

The dfn element contains the defining instance of the enclosed term.

An <dfn id="def-acronym">acronym</dfn> is a word formed
from the initial letters or groups of letters of words in a set phrase
or series of words.

9.5. The em element

The em element indicates emphasis for its contents.

Do <em>not</em> phone before 9 a.m.

9.6. The kbd element

The kbd element indicates text to be entered by the user.

To exit, type <kbd>QUIT</kbd>.

9.7. The l element

The l element represents a semantic line of text (e.g., a line of verse or a line of computer code). It is intended as a structured replacement for the br element.

When visually represented, the l element should start on a new line and have a line break at the end. Whether the line should wrap or not depends on styling properties of the element.

<p class="program">
<l>program p(input, output);</l>
<l>begin</l>
<l>   writeln("Hello world");</l>
<l>end.</l>
</p>

.program { counter-reset: linenumber }
l:before {
    position: relative;
    left: -1em;
    counter-increment: linenumber;
    content: counter(linenumber);
}

9.8. The quote element

This element designates an inline text fragment of quoted text.

Visual user agents must not by default add delimiting quotation marks (as was the case for the q element in earlier versions of XHTML). It is the responsibility of the document author to add any required quotation marks, either directly in the text, or via a stylesheet.

<p>John said, <quote>"I saw Lucy at lunch, she told me
<quote>'Mary wants you
to get some ice cream on your way home.'</quote> I think I will get
some at Jen and Berry's, on Gloucester Road."</quote></p>

Steven replied:
<quote cite="http://lists.example.org/2002/01.html">We quite agree</quote>

9.9. The samp element

The samp element designates sample output from programs, scripts, etc.

On starting, you will see the prompt <samp>$ </samp>.

9.10. The span element

The span element, in conjunction with the id and class attributes, offer a generic mechanism for adding structure to documents. This element imposes no presentational idioms on the content. Thus, authors may use this element in conjunction with style sheets , the xml:lang attribute, etc., to tailor XHTML to their own needs and tastes.

<p>This operation is called
the <span class="xref">transpose</span>
or <span class="xref">inverse</span>.</p>

9.11. The strong element

The strong element indicates higher importance for its contents.

On <strong>Monday</strong> please put the rubbish out,
but <em>not</em> before nightfall!

9.12. The sub element

The sub element indicates that its contents should regarded as a subscript.

For visual user agents this element would normally be rendered as a subscript of the text baseline, but on user agents where this is not possible (for instance teletype-like devices) other renderings may be used. For instance, a<sub>i, j</sub> that would be rendered as a i, j on a device that can render it so, might be rendered as a[i, j] on a simpler device.

      H<sub>2</sub>O

9.13. The sup element

The sup element indicates that its contents should be regarded as a super-script.

For visual user agents this element would normally be rendered as a super-script of the text baseline, but on user agents where this is not possible (for instance teletype-like devices) other renderings may be used. For instance, 2<sup>n</sup> that would be rendered as 2 n on a device that can render it so, might be rendered as 2↑(n) on a simpler device.

Many scripts (e.g., French) require superscripts or subscripts for proper rendering. The sub and sup elements should be used to markup text in these cases.

      H<sub>2</sub>O
      E = mc<sup>2</sup>
      <span xml:lang="fr">M<sup>lle</sup> Dupont</span>

9.14. The var element

The var element indicates an instance of a variable or program argument.

The parameter <var>ncols</var> represents
the number of colors to use.

10. XHTML Hypertext Module

This section is normative .

The Hypertext Module provides an element that traditionally has been used in HTML to define hypertext links to other resources. Although all elements may now play the role of a hyperlink (using the href attribute) or hyperlink anchor (using the id attribute), this element remains for explicit markup of links, though is otherwise identical in semantics to the span element.

This module supports the following element:

This module adds the a element to the Inline content set of the Inline Text Module.

Implementation: RELAX NG

10.1. The a element

An a element defines an anchor.

1. The a element's content defines the position of the anchor.
2. An href attribute makes this anchor the source anchor of exactly one link.
3. An id attribute makes this anchor the possible target of other links.

Authors may also create an a element that specifies no anchors, i.e., that doesn't specify href , or id . Values for these attributes may be set at a later time through scripts as defined in the Scripting module.

For more information about W3C, please consult the 
<a href="http://www.w3.org/">W3C Web site</a>. 

For more information about W3C, please consult the W3C Web site.
                                                   ~~~~~~~~~~~~

...text before the anchor...
<a id="anchor-one">This is the location of anchor one.</a>
...text after the anchor...

...text before the link...
For more information, please consult <a href="./one.html#anchor-one"> anchor one</a>.
...text after the link...

I just returned from vacation! Here's a
<a id="anchor-two" 
   href="http://www.somecompany.com/People/Ian/vacation/family.png">
photo of my family at the lake.</a>.

11. XHTML List Module

This section is normative .

As its name suggests, the List Module provides list-oriented elements. Specifically, the List Module supports the following elements and attributes:

This module also defines the content set List with the minimal content model (dl | nl | ol | ul)+ and adds this set to the Flow content set of the Block Text Module.

Implementation: RELAX NG

XHTML offers authors several mechanisms for specifying lists of information. All lists must contain one or more list elements. Lists may contain:

• Unordered information.
• Ordered information.
• Navigation information.
• Definitions.

The previous list, for example, is an unordered list, created with the ul element:

<ul>
<li>Unordered information. </li>
<li>Ordered information. </li>
<li>Navigation information. </li>
<li>Definitions. </li>
</ul>

An ordered list, created using the ol element, should contain information where order should be emphasized, as in a recipe:

1. Mix dry ingredients thoroughly.
2. Pour in wet ingredients.
3. Mix for 10 minutes.
4. Bake for one hour at 300 degrees.

Definition lists, created using the dl element, generally consist of a series of term/definition pairs (although definition lists may have other applications). Thus, when advertising a product, one might use a definition list:

Lower cost

The new version of this product costs significantly less than the previous one!

Easier to use

We've changed the product so that it's much easier to use!

Safe for kids

You can leave your kids alone in a room with this product and they won't get hurt (not a guarantee).

defined in XHTML as:

<dl>
<dt><strong>Lower cost</strong></dt>
<dd>The new version of this product costs significantly less than the
previous one!</dd>
<dt><strong>Easier to use</strong></dt>
<dd>We've changed the product so that it's much easier to
use!</dd>
<dt><strong>Safe for kids</strong></dt>
<dd>You can leave your kids alone in a room with this product and
they won't get hurt (not a guarantee).</dd>
</dl>

Lists may also be nested and different list types may be used together, as in the following example, which is a definition list that contains an unordered list (the ingredients) and an ordered list (the procedure):

The ingredients:

• 100 g. flour
• 10 g. sugar
• 1 cup water
• 2 eggs
• salt, pepper

The procedure:

1. Mix dry ingredients thoroughly.
2. Pour in wet ingredients.
3. Mix for 10 minutes.
4. Bake for one hour at 300 degrees.

Notes:

The recipe may be improved by adding raisins.

The exact presentation of the three list types depends on the user agent and/or the stylesheet in effect. Authors must not use lists purely as a means of indenting text. This is a stylistic issue and is properly handled by style sheets.

11.1. Definition lists: the dl , dt , and dd elements

Definition lists vary only slightly from other types of lists in that list items consist of two parts: a term and a description. The term is given by the dt element and is restricted to inline content. The description is given with a dd element that contains block-level content.

  
<dl>
  <dt>Dweeb</dt>
  <dd>young excitable person who may mature
    into a <em>Nerd</em> or <em>Geek</em></dd>
  <dt>Hacker</dt>
  <dd>a clever programmer</dd>
  <dt>Nerd</dt>
  <dd>technically bright but socially inept person</dd>
</dl>

<dl>
   <dt>Center</dt>
   <dt>Centre</dt>
   <dd> A point equidistant from all points
              on the surface of a sphere.</dd>
   <dd> In some field sports, the player who
              holds the middle position on the field, court,
              or forward line.</dd>
</dl>

Another application of dl , for example, is for marking up dialogues, with each dt naming a speaker, and each dd containing his or her words.

11.2. The nl element

Navigation lists are intended to be used to define collections of selectable items for presentation in a "navigation" menu. A navigation list is required to start with a label element that defines the label for the list.

On visual user agents, the default presentation behavior is as follows:

1. The contents of the label element are presented.
2. When the label element's content is selected, the navigation list's li element contents are displayed.
3. If an li element contains another navigation list , that list's label's contents are displayed.
4. If an li element has an href attribute, and that element's contents are selected, the link defined by the href attribute is followed.
5. If the nl element is de-selected, it's contents are removed from the display.

It is possible to change this default behavior through the use of style sheets. The behavior of navigation lists in non-visual user agents is unspecified.

<nl>
   <label>Contents </label>
   <li href="#introduction">Introduction</li>
   <li>
      <nl>
          <label>Terms</label>
          <li href="#may">May</li>
          <li href="#must">Must</li>
          <li href="#should">Should</li>
      </nl>
   </li>
   <li href="#conformance">Conformance</li>
   <li href="#references">References</li>
   ...
</nl>

11.3. The ol , and ul elements

Ordered and unordered lists are rendered in an identical manner except that visual user agents number ordered list items. User agents may present those numbers in a variety of ways. Unordered list items are not numbered.

Both types of lists are made up of sequences of list items defined by the li element.

<ul>
   <li> ... first list item...</li>
   <li> ... second list item...</li>
   ...
</ul>

11.4. The li element

The li element defines a list item within an ordered, unordered, or navigation list. When the href attribute is defined, the contents of the list item become a selectable link, just as an a element with an href attribute would be.

11.5. The label element

The label element is used to define a label for an nl navigation list. The contents of the label element are displayed as the title of a list (or sublist). See nl for more information.

12. XHTML Linking Module

This section is normative .

The Link Module defines an element that can be used to define links to external resources. These resources are often used to augment the user agent's ability to process the associated XHTML document. The element and attributes included in this module are:

When this module is used, it adds the link element to the content model of the head element as defined in the Structure Module .

Implementation: RELAX NG

12.1. The link element

This element defines a link. Unlike a , it may only appear in the head section of a document, although it may appear any number of times. Although link has no content, it conveys relationship information that may be rendered by user agents in a variety of ways (e.g., a tool-bar with a drop-down menu of links).

<head>
  <title>Chapter 2</title>
  <link rel="Index" href="../index.html"/>
  <link rel="Next"  href="Chapter3.html"/>
  <link rel="Prev"  href="Chapter1.html"/>
</head>

12.1.1. Forward and reverse links

While the rel attribute specifies a relationship from this document to another resource, the rev attribute specifies the reverse relationship.

Consider two documents A and B.

Document A:       <link href="docB" rel="index"/>

Has exactly the same meaning as:

Document B:       <link href="docA" rev="index"/>

namely that document B is the index for document A.

Both the rel and rev attributes may be specified simultaneously.

12.1.2. Links and external style sheets

When the link element links an external style sheet to a document, the type attribute specifies the style sheet language and the media attribute specifies the intended rendering medium or media. User agents may save time by retrieving from the network only those style sheets that apply to the current device.

Media descriptors are further discussed under Attribute Types.

12.1.3. Links and search engines

Authors may use the link element to provide a variety of information to search engines, including:

• Links to alternate versions of a document, written in another human language.
• Links to alternate versions of a document, designed for different media, for instance a version especially suited for printing.
• Links to the starting page of a collection of documents.

The examples below illustrate how language information, media types, and link types may be combined to improve document handling by search engines.

<head>
<title>The manual in English</title>
<link title="The manual in Dutch"
      rel="alternate"
      xml:lang="nl" 
      href="http://example.com/manual/dutch.html"/>
<link title="The manual in Portuguese"
      rel="alternate"
      xml:lang="pt" 
      href="http://example.com/manual/portuguese.html"/>
<link title="The manual in Arabic"
      rel="alternate"
      xml:lang="ar" 
      href="http://example.com/manual/arabic.html"/>
<link lang="fr" title="La documentation en Fran&ccedil;ais"
      rel="alternate"
      xml:lang="fr"
      href="http://example.com/manual/french.html"/>
</head>

<head>
<title>Reference manual</title>
<link media="print" 
      title="The manual in PostScript"
      type="application/postscript"
      rel="alternate"
      href="http://example.com/manual/postscript.ps"/>
</head>

<head>
<title>Reference manual -- Chapter 5</title>
<link rel="Start" title="The first chapter of the manual"
      type="text/html"
      href="http://example.com/manual/start.html"/>
</head>

13. XHTML Metainformation Module

This section is normative .

The Metainformation Module defines an element that describes information within the declarative portion of a document (in XHTML within the head element). This module includes the following element:

When this module is selected, the meta element is added to the content model of the head element as defined in the Structure Module.

Implementation: RELAX NG

13.1. The meta element

For the following attributes, the permitted values and their interpretation are profile dependent:

The meta element can be used to identify properties of a document (e.g., author, expiration date, a list of key words, etc.) and assign values to those properties. This specification does not define a normative set of properties.

Each meta element specifies a property/value pair. The name attribute identifies the property and the content of the element specifies the property's value.

<meta name="Author">Steven Pemberton</meta>

<meta name="DC.identifier">http://www.rfc-editor.org/rfc/rfc3236.txt</meta>

<link rel="DC.identifier"
         type="text/plain"
         href="http://www.rfc-editor.org/rfc/rfc3236.txt"/>

13.1.1. meta and search engines

A common use for meta is to specify keywords that a search engine may use to improve the quality of search results. When several meta elements provide language-dependent information about a document, search engines may filter on the xml:lang attribute to display search results using the language preferences of the user. For example,

<!-- For speakers of US English -->
<meta name="keywords" xml:lang="en-us">vacation, Greece, sunshine</meta>
<!-- For speakers of British English -->
<meta name="keywords" xml:lang="en">holiday, Greece, sunshine</meta>
<!-- For speakers of French -->
<meta name="keywords" xml:lang="fr">vacances, Gr&egrave;ce, soleil</meta>

The effectiveness of search engines can also be increased by using the link element to specify links to translations of the document in other languages, links to versions of the document in other media (e.g., PDF), and, when the document is part of a collection, links to an appropriate starting point for browsing the collection.

13.1.2. meta and RDF

13.1.3. meta data profiles

The profile attribute of the html element specifies the location of a meta data profile. The value of the profile attribute is a URI. User agents may use this URI in two ways:

• As a globally unique name. User agents may be able to recognize the name (without actually retrieving the profile) and perform some activity based on known conventions for that profile. For instance, search engines could provide an interface for searching through catalogs of XHTML documents, where these documents all use the same profile for representing catalog entries.
• As a link. User agents may dereference the URI and perform some activity based on the actual definitions within the profile (e.g., authorize the usage of the profile within the current XHTML document). This specification does not define formats for profiles.

 <html ... profile="http://www.acme.com/profiles/core">
  <head>
      <title>How to complete Memorandum cover sheets</title>
      <meta name="author">John Doe</meta>
      <meta name="copyright">&copy; 1997 Acme Corp.</meta>
      <meta name="keywords">corporate,guidelines,cataloging</meta>
      <meta name="date">1994-11-06T08:49:37+00:00</meta>
 </head>
...

14. XHTML Object Module

This section is normative .

The Object Module provides elements for general-purpose object inclusion; this includes images and other media, as well as executable content. Specifically, the Object Module supports:

When this module is used, it adds the object element to the Inline content set of the Inline Text module.

Implementation: RELAX NG

14.1. The object element

14.1.1. Defining terminology

The following terms will be used throughout this section.

object data

The file that is to be processed, such as an mp3, or a .gif file. The actual content to be processed.

object handler

The mechanism that will be used to process the object data. The mechanism could be the user agent or an external application.

object element

This refers to the actual XHTML coding, including the allowable attributes.

instantiation

Refers to the plug-in handler, and the need to create a window, modify the user interface, allocate memory, etc.

14.1.2. Basic Information for Object Handlers

Most user agents have built-in mechanisms for processing common data types such as text, and various image types (gif, jpg and png for example) in some instances the user agent may pass the processing to an external application. Generally, a user agent will attempt to process the object declaration, otherwise it may invoke an external application, which are normally referred to as "plug-ins".

In the most general case, an author should specify three types of information:

• The location of the object data (the data attribute). The author must direct the object handler to the actual physical location of the object data, otherwise the object handler will not be able to process the request.
• The mime type associated with the object data (the type attribute). For instance, if the author prefers that a particular object handler be used to process the data, they may specify a mime type that is associated to a specific object handler.
• Additional values required for the appropriate processing of the object data by the object handler at run-time (via the param element). Some instances may process more appropriately if the object handler is passed initial process instructions. For example, the author can specify whether a video should automatically start or wait until the entire data file has been downloaded.

The object element allows authors to specify all three types of information, but authors may not have to specify all three at once. For example, some object element instances may not require data (e.g., a self-contained applet that performs a small animation). Others may not require mime type information, i.e., the user agent itself may already know how to process that type of data (e.g., GIF images). Still others may not require run-time initialization.

Authors specify an object's mime type and the location of the data to be processed via the object element. To specify run-time values, however, authors use the param element, which is discussed in the section on object initialization.

The object element may also appear in the content of the head element. Since user agents generally do not process elements in the head , authors should ensure that any object element in the head does not specify content that may be processed. Please consult the section on sharing frame data for an example of including the object element in the head element.

Please consult the section on form controls for information about object elements in forms.

14.1.3. Rules for processing objects

A user agent must interpret an object element according to the following precedence rules:

1. The user agent must first try to process the object element. It should not process the embedded contents, but it must examine them in case there are param elements (see object initialization) or elements that take advantage of the Map attribute collection defined.
2. If the user agent is not able to process the object for whatever reason (configured not to, lack of resources, wrong architecture, etc.), it must try to process its contents.

Authors should not include content in object elements that appear in the head element.

When a user agent is able to successfully process an object element it MUST not attempt to process inner elements. For example, if the following code is encountered:

<object ... pointing to objectdataA>
<object ... pointing to objectdataB>
<p>alternate text</p>
</object>
</object>

When the user agent encounters objectdataA and is able to process that object element, then all nested elements (except for applicable param elements) MUST be ignored.

If a user agent cannot process an object element or a set of nested objects, and the author did not provide alternate text, the user agent SHOULD NOT supply any additional information. It is the responsibility of the author to supply additional or alternate information. It may be the intent of the author to not provide additional information if the object cannot be processed.

The user agent SHOULD attempt to process the outer object to its fullest extent before dropping to a nested object. For example, if the author provided information that could be used to download an external application to be used to process the object, then the user agent SHOULD attempt to download and install the application. If the user selects to not install the application, the user agent SHOULD continue to process the nested object or objects, if they exist.

<object data="http://www.example.com/foo.mp3" type="audio/mpeg">
   <em>alternate text</em>
</object>

<object data="http://www.example.com/foo.jpg" type="image/jpeg">
   <em>alternate text</em>
</object>

<applet

  codebase="http://www.example.com/applets/classes"  
  code="Clock.class"
  width="150" 
  height="150">
    <param name="bgcolor" value="ffffff"/>
    <param name="border" value="5"/>
    <param name="ccolor" value="dddddd"/>
    <param name="cfont" value="TimesRoman|BOLD|18"/>
    <param name="delay" value="100"/>
    <param name="hhcolor" value="0000ff"/>

    <param name="link" value="http://www.example.com/"/>
    <param name="mhcolor" value="00ff00"/>
    <param name="ncolor" value="000000"/>
    <param name="nradius" value="80"/>
    <param name="shcolor" value="ff0000"/>
</applet>

<style type="text/css">
#obj1 {width:150px; height:150px;}

</style>
...
<object id="obj1" 
  xml:base="http://www.example.com/applets/classes" 
  type="application/x-java-applet" 
  data="Clock.class">
    <param  name="delay"   value="100"/>
    <param  name="link"    value="http://www.example.com/"/>
    <param  name="border"  value="5"/>
    <param  name="nradius" value="80"/>
    <param  name="cfont"   value="TimesRoman|BOLD|18"/>
    <param  name="bgcolor" value="ddddff"/>
    <param  name="shcolor" value="ff0000"/>
    <param  name="mhcolor" value="00ff00"/>
    <param  name="hhcolor" value="0000ff"/>
    <param  name="ccolor"  value="dddddd"/>
    <param  name="ncolor"  value="000000"/>
    <em>alternate text</em>
</object>

Authors should always include alternate text as the content of the object element declaration when an embedded object is not defined. If an author includes alternate text and an embedded object, the object handler may process both the text and the embedded object. The alternate text will provide the user a hint in cases where the object handler cannot process the object data. The author should also consider supplying a link to the location where the external application may be downloaded in case the user does not have the external application installed.

<object data="http://www.example.com/foo.mp3" type="audio/mpeg">
   A really cool audio file. If you want to download and install 
   a plug-in to listen to this file, please go to 
   <a href="http://www.example.com">www.example.com</a>

</object>

One significant consequence of the object element's design is that it offers a mechanism for specifying alternate object processing; each embedded object element declaration may specify alternate content types. If the object handler cannot process the outermost object , it must then process the embedded contents, which may be another object element, etc. In this case, the innermost object element declaration should contain alternative text, the outer object element declarations should not contain alternative text since an embedded object element declaration is present.

<!-- First, try the applet -->
<object 
    data="http://www.example.com/TheEarth.class"
    type="application/x-java-applet">
      <!-- Else, try the MPEG video -->
      <object 
          data="TheEarth.mpeg"
          type="video/mpeg"
          xml:base="http://www.example.com/">
            <!-- Else, try the GIF image -->
            <object
                data="TheEarth.gif"
                type="image/gif"
                xml:base="http://www.example.com/">
                <!-- Else process the alternate text -->
                The <strong>Earth</strong> as seen from space.
            </object>
      </object>
</object>

Another way to approach the usage of the object element attributes is this way:

<object 
    id="clock1"
    type="application/x-java-applet">
    A clock.
</object>

14.2. The param element

param elements specify a set of values that may be required to process the object data by an object handler at run-time. Any number of param elements may appear in the content of an object element, in any order, but must be placed at the start of the content of the enclosing object element, with the exception of optional caption and standby elements.

The syntax of names and values is assumed to be understood by the user agent or the external application that will process the object data. This document does not specify how object handlers should retrieve name/value pairs nor how they should interpret parameter names that appear twice.

The user agent or the external application can utilize the param element name/value pairs to pass unique datapoints to trigger specific functions or actions. For example, the user agent may wish to trigger an external application download if the user does not have an appropriate application installed on their system.

    
<object 
    data="http://www.example.com/myclock.class"
    type="application/x-java-applet">
        <param name="height" value="40" valuetype="data" />
        <param name="width" value="40" valuetype="data" />
        This user agent cannot process a java applet.
</object>

<object
    data="http://www.example.com/gifappli"
    type="image/gif">
        <standby>Loading Elvis...</standby>

        <param name="Init_values"
            value="./images/elvis.gif"
            valuetype="ref" />
        Elvis lives!
</object>

When an object element is processed, the user agent must search the content for only those param elements that are direct children and "feed" them to the object handler.

<object
    data="obj1"
    type="application/x-something">
    <param name="param1" value="value1" />
    <object
        data="obj2"
        type="application/x-something">
        <param name="param2" value="value2" />
        This user agent cannot process this application.
    </object>
</object>

14.2.1. Referencing object data

The location of an object's data is given by a URI. The URI may be either an absolute URI or a relative URI. If the URI is relative, it may be based from the referring document location or from the xml:base attribute location.

<object
    data="mymovie.mpg"
    type="video/mpeg">
    A film showing how to open the printer to replace the cartridge.
</object>

By setting the type attribute, a user agent can determine whether to retrieve the external application based on its ability to do so. The location of the object data is relative to the referencing document, in this example the object data would need to exist within the same directory.

<object
    xml:base="http://www.example.com/"
    data="mymovie.mpg"
    type="video/mpeg">
    This user agent cannot process this movie.
</object>

14.2.2. Object element declarations and instantiations

The following example is for illustrative purposes only. When a document is designed to contain more than one instance of the same object data, it is possible to separate the declaration of the object from the references to the object data. Doing so has several advantages:

• The object data may be retrieved from the network by the object handler one time (during the declaration) and reused for each additional reference to that object data.
• It is possible to reference the object data from a location other than the object element in which it was defined, for example, from a link.
• It is possible to specify an object data as run-time data for other object element declarations.

To declare an object element so that it is not executed when read by the object handler, set the boolean declare attribute in the object element. At the same time, authors must identify the object declaration by setting the id attribute in the object element to a unique value. Later processing of the object data will refer to this identifier.

A declared object element must appear in a document before the first time the object data is referenced. For example, the delaring object element must appear before a link referencing the object data.

When an object element is defined with the declare attribute, the object handler is instantiated every time an element refers to that object data later in the document. The references will require the object data to be processed (e.g., a link that refers to it is activated, an object element that refers to it is activated, etc.).

<object
    declare="declare"
    id="earth.declaration" 
    data="TheEarth.mpg" 
    type="video/mpeg">
    The <strong>Earth</strong> as seen from space.
</object>
...later in the document...
<p>A neat <a href="#earth.declaration">animation of The Earth!</a></p>

User agents that do not support the declare attribute must process the contents of the object element.

14.3. The standby element

The standby element specifies a message that a user agent may render while loading the object's implementation and data.

15. Ruby Module

This section is informative .

The Ruby Module defines elements for ruby annotation markup as defined in Ruby Annotation [ RUBY ].

This module adds the ruby element to the Inline content set of the Inline Text Module. XHTML 2.0 supports the maximal content model for the ruby element, defined as follows:

((rb, (rt | (rp, rt, rp))) | (rbc, rtc, rtc?))

As defined in [ RUBY ], the ruby element is not allowed to nest.

Implementation: RELAX NG ,DTD

16. XHTML Scripting Module

This section is normative .

The Scripting Module defines elements that are used to contain information pertaining to executable scripts or the lack of support for executable scripts. Elements and attributes included in this module are:

When this module is used, the script and noscript elements are added to the Block and Inline content sets of the Block and Inline Text Modules. In addition, the script element is added to the content model of the head element defined in the Structure Module.

Implementation: RELAX NG

16.1. The noscript element

The noscript element allows authors to provide alternate content when a script is not executed. The content of a noscript element will be rendered if and only if the containing script is not processed. noscript elements that are not contained in a script element will only be rendered in the following cases:

• The user agent is configured not to evaluate scripts.
• The user agent doesn't support a scripting language invoked by a script element earlier in the document.
• The user agent can't access an external script.

User agents that do not support client-side scripts must render this element's contents.

<script type="text/tcl" src="http://example.org/script">
 <noscript>
  <p>Access the <a href="http://example.org/data">data.</a></p>
 </noscript>
</script>

16.2. The script element

The script element places a script within a document. This element may appear any number of times in the head or body of an XHTML document.

The script may be defined within the contents of the script element or in an external file. If the src attribute is not set, user agents must interpret the contents of the element as the script. If the src has a URI value, user agents must ignore the element's contents and retrieve the script via the URI. Note that the charset attribute refers to the character encoding of the script designated by the src attribute; it does not concern the content of the script element.

16.2.1. Rules for processing scripts

Scripts are evaluated by script engines that must be known to a user agent.

A user agent must interpret a script element according to the following precedence rules:

1. The user agent must first try to process the script element, but not the embedded content.
2. If the user agent is not able to process the script for any reason (configured not to, no support of the scripting language, no access to an external resource, etc.), it must try to process its contents.
3. If the content is inline text it must be evaluated as script data of the scripting language of the containing script element.
4. If the content is a noscript element, its content should be rendered.
5. If the content is a script element, its content should be processed according to these rules.

The syntax of script data depends on the scripting language.

16.2.2. Specifying the scripting language

As XHTML does not rely on a specific scripting language, document authors must explicitly tell user agents the language of each script. This may be done either through a default declaration or a local declaration.

16.2.3. Declaration of a scripting language

The type attribute must be specified for each script element instance in a document.

<html xmlns="http://www.w3.org/2002/06/xhtml2">
 <head>
  <title>A document with script</title>
  <script type="text/x-vbscript" src="http://example.org/progs/vbcalc">
   <script type="text/javascript">
    ...some inline JavaScript...
   </script>
  </script>
 </head>
 <body>
    <script type="text/x-perl"/>
 </body>
</html>

16.2.4. Dynamic modification of documents

Note that because of the XML processing model, where a document is first parsed before being processed, the form of dynamic generation used in earlier versions of HTML, using document.write cannot be used in XHTML2. To dynamically generate content in XHTML you have to add elements to the DOM tree using DOM calls [ DOM ] rather than using document.write top generate text that then gets parsed.

17. XHTML Style Attribute Module

This section is normative .

The Style Attribute Module defines the style attribute. When this module is selected, it activates the Style Collection.

Note: use of the style attribute is strongly discouraged in favor of the style element and external style sheets. In addition, content developers are advised to avoid use of the style attribute on content intended for use on small devices, since those devices may not support the use of in-line styles.

Implementation: RELAX NG

style = CDATA

This attribute specifies style information for the current element.

The syntax of the value of the style attribute is determined by the default style sheet language. For example, for [ CSS2 ] inline style, use the declaration block syntax described in the Style Sheet Module (without curly brace delimiters).

This CSS example sets color and font size information for the text in a specific paragraph.

<p style="font-size: 12pt; color: fuchsia">Aren't style sheets wonderful?</p>

In CSS, property declarations have the form "name : value" and are separated by a semi-colon.

To specify style information for more than one element, authors should use the style element. For optimal flexibility, authors should define styles in external style sheets.

Style Attributes and Generic XML

There is currently no way to declare what attribute within a given namespace contains "styling" information in a way that a Generic XML processor can discern. In an ideal world, someone would define such a mechanism (e.g., through the xml-stylesheet PI).

18. XHTML Style Sheet Module

This section is normative .

The Style Sheet Module defines an element to be used when declaring internal style sheets. The element and attributes defined by this module are:

When this module is used, it adds the style element to the content model of the head element of the Structure Module.

Implementation: RELAX NG

18.1. The style element

The style element allows an author to put style sheet rules in the head of the document. XHTML permits any number of style elements in the head section of a document.

User agents that don't support style sheets, or don't support the specific style sheet language used by a style element, must hide the contents of the style element. It is an error to render the content as part of the document's text.

The syntax of style data depends on the style sheet language.

Rules for style rule precedences and inheritance depend on the style sheet language.

<head>
 <style type="text/css">
   h1 {border-width: thin; border-style: solid; text-align: center}
 </style>
</head>

18.1.1. External style sheets

Authors may separate style sheets from XHTML documents. This offers several benefits:

• Authors and web site managers may share style sheets across a number of documents (and sites).
• Authors may change the style sheet without requiring modifications to the document.
• User agents may load style sheets selectively (based on media descriptors).

18.1.2. Preferred and alternate style sheets

XHTML allows authors to associate any number of external style sheets with a document. The style sheet language defines how multiple external style sheets interact (for example, the CSS "cascade" rules).

Authors may specify a number of mutually exclusive style sheets called alternate style sheets. Users may select their favorite among these depending on their preferences. For instance, an author may specify one style sheet designed for small screens and another for users with weak vision (e.g., large fonts). User agents should allow users to select from alternate style sheets.

The author may specify that one of the alternates is a preferred style sheet. User agents should apply the author's preferred style sheet unless the user has selected a different alternate.

Authors may group several alternate style sheets (including the author's preferred style sheets) under a single style name . When a user selects a named style, the user agent must apply all style sheets with that name. User agents must not apply alternate style sheets with a different style name. The section on specifying external style sheets explains how to name a group of style sheets.

Authors may also specify persistent style sheets that user agents must apply in addition to any alternate style sheet.

User agents must respect media descriptors when applying any style sheet.

User agents should also allow users to disable the author's style sheets entirely, in which case the user agent must not apply any persistent or alternate style sheets.

18.1.3. Specifying external style sheets

Authors specify external style sheets with the following attributes of the link element:

• Set the value of href to the location of the style sheet file. The value of href is a URI .
• Set the value of the type attribute to indicate the language of the linked (style sheet) resource. This allows the user agent to avoid downloading a style sheet for an unsupported style sheet language.
• Specify that the style sheet is persistent, preferred, or alternate:
  • To make a style sheet persistent, set the rel attribute to "stylesheet" and don't set the title attribute.
  • To make a style sheet preferred, set the rel attribute to "stylesheet" and name the style sheet with the title attribute.
  • To specify an alternate style sheet, set the rel attribute to "alternate stylesheet" and name the style sheet with the title attribute.

User agents should provide a means for users to view and pick from the list of alternate styles. The value of the title attribute is recommended as the name of each choice.

<link href="mystyle.css" rel="stylesheet" type="text/css"/>

 <link href="mystyle.css" title="compact" rel="stylesheet" type="text/css"/>

<link href="mystyle.css" title="Medium" rel="alternate stylesheet" type="text/css"/>

For more information on external style sheets, please consult the section on links and external style sheets.

If two or more link elements specify a preferred style sheet, the first one takes precedence.

19. XHTML Tables Module

This section is normative .

The Tables Module provides elements for marking up tabular information in a document.

The module supports the following elements, attributes, and content model:

When this module is used, it adds the table element to the Block content set of the Block Text Module.

Implementation: RELAX NG

19.1. The caption element

When present, the caption element's text should describe the nature of the table or the object. The caption element is only permitted immediately after the table start tag or the object start tag. A table element or an object element may only contain one caption element.

For tables, visual user agents allow sighted people to quickly grasp the structure of the table from the headings as well as the caption. A consequence of this is that captions will often be inadequate as a summary of the purpose and structure of the table from the perspective of people relying on non-visual user agents.

Authors should therefore take care to provide additional information summarizing the purpose and structure of the table using the summary element. This is especially important for tables without captions. The example below illustrates the use of the summary element.

User agents must provide access to the content of the summary element. As an example, access could be provided through a menu option, a mouse-over function, or through a dialog.

<table>
  <caption>Student Class Roster</caption>
  <summary>The table defines the class roster.
    The columns contain the following data:
    students name, permanent address, permanent phone,
    local address, local phone,
    declared major, assigned academic advisor,
    student standing</summary>
  ...the rest of the table...

</table>

19.1.1. Caption Clipping

Visual user agents must avoid clipping any part of the table including the caption, unless a means is provided to access all parts, e.g., by horizontal or vertical scrolling. We recommend that the caption text be wrapped to the same width as the table.

19.2. The col and colgroup elements

The colgroup element allows authors to create structural divisions within a table. Authors may highlight this structure through style sheets. For example, the author may wish to divide the columns into logical groups such as the student's permanent address, phone number and emergency contact information. And group the student's local address, phone and email address into another logical group.

A table may either contain a single implicit column group (no colgroup element delimits the columns) or any number of explicit column groups (each delimited by an instance of the colgroup element).

The col element allows authors to share attributes among several columns without implying any structural grouping. The "span" of the col element is the number of columns that will share the element's attributes. For example, the author may wish to apply a specific style to the student's permanent data and apply a different style to the student's local data.

The colgroup element creates an explicit column group. The number of columns in the column group may be specified in two, mutually exclusive ways:

1. The colgroup span attribute (default value 1) specifies the number of columns in the group.
2. Each embedded col element in the colgroup represents one or more columns in the group.

The advantage of using the colgroup element is that authors may logically group multiple columns. By grouping columns, the author can apply rules across the entire group. The author can also apply column width balancing across the group of columns. For example, if the author has a table with five columns and the author divides the table into two column groups, one with three columns and the other with two columns. The author could define the first column group to consume 300 pixels and the second column group to consume 100 pixels. Each column within the first column group would be 100 pixels wide and the remaining two columns would be 50 pixels wide. If the author added embedded col elements, she could force one or more columns to be a specific width and the remaining columns within the group would be evenly divided within the remaining allotted width.

<style type="text/css">
#colgrp1 { width: 300px }
#col1 { width: 100px }
#col2 { width: 50px }

</style>
...
<table>
  <colgroup id="colgrp1">
    <col id="col1" span="3"/>
    <col id="col2" span="2"/>

  </colgroup>
...the rest of the table...
</table>

When it is necessary to single out a column (e.g., for style information, to specify width information, etc.) within a group, authors must identify that column with a col element.

The col element allows authors to group together attribute specifications for table columns. The col does not group columns together structurally -- that is the role of the colgroup element. col elements are empty and serve only as a support for attributes. They may appear inside or outside an explicit column group (i.e., colgroup element).

19.2.1. Calculating the number of columns in a table

There are two ways to determine the number of columns in a table (in order of precedence):

1. If the table element contains any colgroup or col elements, user agents should calculate the number of columns by summing the following:
   • For each col element, take the value of its span attribute (default value 1).
   • For each colgroup element containing at least one col element, ignore the span attribute for the colgroup element. For each col element, perform the calculation of step 1.
   • For each empty colgroup element, take the value of its span attribute (default value 1).
2. Otherwise, if the table element contains no colgroup or col elements, user agents should base the number of columns on what is required by the rows. The number of columns is equal to the number of columns required by the row with the most columns, including cells that span multiple columns. For any row that has fewer than this number of columns, the end of that row should be padded with empty cells. The "end" of a row depends on the directionality of a table .

It is an error if a table contains colgroup or col elements and the two calculations do not result in the same number of columns.

Once the user agent has calculated the number of columns in the table, it may group them into a colgroup .

19.3. The summary element

This element provides a summary of the table's purpose and structure for user agents rendering to non-visual media such as speech and Braille.

19.4. The table element

The table element contains all other elements that specify the caption, column groups, columns, rows, and content for a table.

19.4.1. Visual Rendering

The following informative list describes what operations visual user agents may carry out when rendering a table:

• Provide access to the content of the summary element. As an example, access could be provided through a menu option, a mouse-over function, or through a dialog. Authors should provide a summary of a table's content and structure so that people using non-visual user agents may better understand it.
• Render the caption, if one is defined. The caption may be rendered, for example, either on the top or the bottom of the table.
• Render the table header, if one is specified. Render the table footer, if one is specified. User agents must know where to render the header and footer. For instance, if the output medium is paged, user agents may put the header at the top of each page and the footer at the bottom. Similarly, if the user agent provides a mechanism to scroll the rows, the header may appear at the top of the scrolled area and the footer at the bottom.
• Calculate the number of columns in the table. Note that the number of rows in a table is equal to the number of tr elements contained by the table element.
• Group the columns according to any column groups specifications.
• Render the cells, row by row and grouped in appropriate columns, between the header and footer. Visual user agents should format the table according to XHTML attributes and style sheet specification.

The XHTML table model has been designed so that, with author assistance, user agents may render tables incrementally (i.e., as table rows arrive) rather than having to wait for all the data before beginning to render.

In order for a user agent to format a table in one pass, authors must tell the user agent:

• The number of columns in the table.
• The widths of these columns.

More precisely, a user agent may render a table in a single pass when the column widths are specified using a combination of colgroup and col elements. If any of the columns are specified in relative or percentage terms, authors must also specify the width of the table itself.

19.4.2. Table directionality

The directionality of a table is either the inherited directionality (the default is left-to-right) or that specified by the dir attribute for the table element.

For a left-to-right table, column zero is on the left side and row zero is at the top. For a right-to-left table, column zero is on the right side and row zero is at the top.

When a user agent allots extra cells to a row, extra row cells are added to the right of the table for left-to-right tables and to the left side for right-to-left tables.

Note that table is the only element on which dir reverses the visual order of the columns; a single table row ( tr ) or a group of columns ( colgroup ) cannot be independently reversed.

When set for the table element, the dir attribute also affects the direction of text within table cells (since the dir attribute is inherited by block-level elements).

<table dir="rtl">
...the rest of the table...
</table>

The direction of text in individual cells can be changed by setting the dir attribute in an element that defines the cell.

19.4.3. Table rendering by non-visual user agents

This section provides more detailed discussion on cell header data and how non-visual agents may utilize that information.

19.4.3.1. Associating header information with data cells

Non-visual user agents such as speech synthesizers and Braille-based devices may use the following td and th element attributes to render table cells more intuitively:

• For a given data cell, the headers attribute lists which cells provide pertinent header information. For this purpose, each header cell must be named using the id attribute. Note that it's not always possible to make a clean division of cells into headers or data. You should use the td element for such cells together with the id or scope attributes as appropriate.
• For a given header cell , the scope attribute tells the user agent the data cells for which this header provides information. Authors may choose to use this attribute instead of headers according to which is more convenient; the two attributes fulfill the same function. The headers attribute is generally needed when headers are placed in irregular positions with respect to the data they apply to.
• The abbr attribute specifies an abbreviated header for header cells so that user agents may render header information more rapidly.

<table>

<caption>Cups of coffee consumed by each senator</caption>
<summary>This table charts the number of cups
          of coffee consumed by each senator, the type 
          of coffee (decaf or regular), and whether 
          taken with sugar.</summary>

<tbody>
   <tr>
      <th id="t1">Name</th>
      <th id="t2">Cups</th>
      <th id="t3" abbr="Type">Type of Coffee</th>
      <th id="t4">Sugar?</th>
   </tr>
   <tr>
      <td headers="t1">T. Sexton</td>
      <td headers="t2">10</td>
      <td headers="t3">Espresso</td>
      <td headers="t4">No</td>
   </tr>
   <tr>
      <td headers="t1">J. Dinnen</td>
      <td headers="t2">5</td>
      <td headers="t3">Decaf</td>
      <td headers="t4">Yes</td>
   </tr>
</tbody>
</table>

Caption: Cups of coffee consumed by each senator
Summary: This table charts the number of cups
         of coffee consumed by each senator, the type 
         of coffee (decaf or regular), and whether 
         taken with sugar.
Name: T. Sexton,   Cups: 10,   Type: Espresso,   Sugar: No
Name: J. Dinnen,   Cups: 5,    Type: Decaf,      Sugar: Yes

<table>

<caption>Cups of coffee consumed by each senator</caption>
<summary>
  This table charts the number of cups
  of coffee consumed by each senator, the type 
  of coffee (decaf or regular), and whether 
  taken with sugar.
</summary>

<tbody>
   <tr>
      <th scope="col">Name</th>
      <th scope="col">Cups</th>
      <th scope="col" abbr="Type">Type of Coffee</th>
      <th scope="col">Sugar?</th>
   </tr>
   <tr>
      <td>T. Sexton</td>
      <td>10</td>
      <td>Espresso</td>
      <td>No</td>
   </tr>
   <tr>
      <td>J. Dinnen</td>
      <td>5</td>
      <td>Decaf</td>
      <td>Yes</td>
</tbody>
</table>

<table>
<summary>
  History courses offered in the community of
  Bath arranged by course name, tutor, summary, 
  code, and fee
</summary>
<thead>

  <tr>
    <th colspan="5" scope="colgroup">Community Courses -- Bath Autumn 1997</th>
  </tr>
</thead>
<tbody>

  <tr>
    <th scope="col" abbr="Name">Course Name</th>
    <th scope="col" abbr="Tutor">Course Tutor</th>
    <th scope="col">Summary</th>
    <th scope="col">Code</th>
    <th scope="col">Fee</th>
  </tr>
  <tr>
    <td scope="row">After the Civil War</td>
    <td>Dr. John Wroughton</td>
    <td>
       The course will examine the turbulent years in England
       after 1646. <em>6 weekly meetings starting Monday 13th
       October.</em>
    </td>
    <td>H27</td>
    <td>&pound;32</td>
  </tr>
  <tr>
    <td scope="row">An Introduction to Anglo-Saxon England</td>
    <td>Mark Cottle</td>
    <td>
       One day course introducing the early medieval
       period reconstruction the Anglo-Saxons and
       their society. <em>Saturday 18th October.</em>
    </td>
    <td>H28</td>
    <td>&pound;18</td>
  </tr>
  <tr>
    <td scope="row">The Glory that was Greece</td>
    <td>Valerie Lorenz</td>
    <td>
     Birthplace of democracy, philosophy, heartland of theater, home of
     argument. The Romans may have done it but the Greeks did it
     first. <em>Saturday day school 25th October 1997</em>
    </td>
    <td>H30</td>
    <td>&pound;18</td>
  </tr>
</tbody>
</table>

19.4.3.2. Categorizing cells

Users browsing a table with a speech-based user agent may wish to hear an explanation of a cell's contents in addition to the contents themselves. One way the user might provide an explanation is by speaking associated header information before speaking the data cell's contents (see the section on associating header information with data cells ).

Users may also want information about more than one cell, in which case header information provided at the cell level (by headers , scope , and abbr ) may not provide adequate context. Consider the following table, which classifies expenses for meals, hotels, and transport in two locations (San Jose and Seattle) over several days:

Users might want to extract information from the table in the form of queries:

• "What did I spend for all my meals?"
• "What did I spend for meals on 25 August?"
• "What did I spend for all expenses in San Jose?"

Each query involves a computation by the user agent that may involve zero or more cells. In order to determine, for example, the costs of meals on 25 August, the user agent must know which table cells refer to "Meals" (all of them) and which refer to "Dates" (specifically, 25 August), and find the intersection of the two sets.

To accommodate this type of query, the table model allows authors to place cell headers and data into categories. For example, for the travel expense table, an author could group the header cells "San Jose" and "Seattle" into the category "Location", the headers "Meals", "Hotels", and "Transport" in the category "Expenses", and the four days into the category "Date". The previous three questions would then have the following meanings:

• "What did I spend for all my meals?" means "What are all the data cells in the "Expenses=Meals" category?
• "What did I spend for meals on 25 August?" means "What are all the data cells in the "Expenses=Meals" and "Date=Aug-25-1997" categories?
• "What did I spend for all expenses in San Jose?" means "What are all the data cells in the "Expenses=Meals, Hotels, Transport" and "Location=San Jose" categories?

Authors categorize a header or data cell by setting the axis attribute for the cell. For instance, in the travel expense table, the cell containing the information "San Jose" could be placed in the "Location" category as follows:

  <th id="a6" axis="location">San Jose</th>

Any cell containing information related to "San Jose" should refer to this header cell via either the headers or the scope attribute. Thus, meal expenses for 25-Aug-1997 should be marked up to refer to id attribute (whose value here is "a6") of the "San Jose" header cell:

  
  <td headers="a6">37.74</td>

Each headers attribute provides a list of id references. Authors may thus categorize a given cell in any number of ways (or, along any number of "headers", hence the name).

Below we mark up the travel expense table with category information:

<table>

<caption>Travel Expense Report</caption>
<summary>
  This table summarizes travel expenses
  incurred during August trips to
  San Jose and Seattle
</summary>

<tbody>
   <tr>
      <th></th>
      <th id="a2" axis="expenses">Meals</th>
      <th id="a3" axis="expenses">Hotels</th>
      <th id="a4" axis="expenses">Transport</th>
      <td>subtotals</td>
   </tr>
   <tr>
      <th id="a6" axis="location">San Jose</th>
      <th></th>
      <th></th>
      <th></th>
      <td></td>
   </tr>
   <tr>
      <td id="a7" axis="date">25-Aug-97</td>
      <td headers="a6 a7 a2">37.74</td>
      <td headers="a6 a7 a3">112.00</td>
      <td headers="a6 a7 a4">45.00</td>
      <td></td>
   </tr>
   <tr>
      <td id="a8" axis="date">26-Aug-97</td>
      <td headers="a6 a8 a2">27.28</td>
      <td headers="a6 a8 a3">112.00</td>
      <td headers="a6 a8 a4">45.00</td>
      <td></td>
   </tr>
   <tr>
      <td>subtotals</td>
      <td>65.02</td>
      <td>224.00</td>
      <td>90.00</td>
      <td>379.02</td>
   </tr>
   <tr>
      <th id="a10" axis="location">Seattle</th>
      <th></th>
      <th></th>
      <th></th>
      <td></td>
   </tr>
   <tr>
      <td id="a11" axis="date">27-Aug-97</td>
      <td headers="a10 a11 a2">96.25</td>
      <td headers="a10 a11 a3">109.00</td>
      <td headers="a10 a11 a4">36.00</td>
      <td></td>
   </tr>
   <tr>
      <td id="a12" axis="date">28-Aug-97</td>
      <td headers="a10 a12 a2">35.00</td>
      <td headers="a10 a12 a3">109.00</td>
      <td headers="a10 a12 a4">36.00</td>
      <td></td>
   </tr>
   <tr>
      <td>subtotals</td>
      <td>131.25</td>
      <td>218.00</td>
      <td>72.00</td>
      <td>421.25</td>
   </tr>
   <tr>
      <th>Totals</th>
      <td>196.27</td>
      <td>442.00</td>
      <td>162.00</td>
      <td>800.27</td>
   </tr>
</tbody>
</table>

Note that marking up the table this way also allows user agents to avoid confusing the user with unwanted information. For instance, if a speech synthesizer were to speak all of the figures in the "Meals" column of this table in response to the query "What were all my meal expenses?", a user would not be able to distinguish a day's expenses from subtotals or totals. By carefully categorizing cell data, authors allow user agents to make important semantic distinctions when rendering.

Of course, there is no limit to how authors may categorize information in a table. In the travel expense table, for example, we could add the additional categories "subtotals" and "totals".

This specification does not require user agents to handle information provided by the axis attribute, nor does it make any recommendations about how user agents may present axis information to users or how users may query the user agent about this information.

However, user agents, particularly speech synthesizers, may want to factor out information common to several cells that are the result of a query. For instance, if the user asks "What did I spend for meals in San Jose?", the user agent would first determine the cells in question (25-Aug-1997: 37.74, 26-Aug-1997:27.28), then render this information. A user agent speaking this information might read it:

   Location: San Jose. Date: 25-Aug-1997. Expenses, Meals: 37.74
   Location: San Jose. Date: 26-Aug-1997. Expenses, Meals: 27.28

or, more compactly:

   San Jose, 25-Aug-1997, Meals: 37.74
   San Jose, 26-Aug-1997, Meals: 27.28

An even more economical rendering would factor the common information and reorder it:

   San Jose, Meals, 25-Aug-1997: 37.74
                    26-Aug-1997: 27.28

User agents that support this type of rendering should allow authors a means to customize rendering (e.g., through style sheets).

19.4.3.3. Algorithm to find heading information

In the absence of header information from either the scope or headers attribute, user agents may construct header information according to the following algorithm. The goal of the algorithm is to find an ordered list of headers. (In the following description of the algorithm the table directionality is assumed to be left-to-right.)

• First, search left from the cell's position to find row header cells. Then search upwards to find column header cells. The search in a given direction stops when the edge of the table is reached or when a data cell is found after a header cell.
• Row headers are inserted into the list in the order they appear in the table. For left-to-right tables, headers are inserted from left to right.
• Column headers are inserted after row headers, in the order they appear in the table, from top to bottom.
• If a header cell has the headers attribute set, then the headers referenced by this attribute are inserted into the list and the search stops for the current direction.
• td cells that set the axis attribute are also treated as header cells.

19.4.4. Sample table

This sample illustrates grouped rows and columns.

<table>
<caption>Calendar for 2002</caption>
<summary>
  Calendar for 2002. @@need better summary
</summary>
<colgroup span="7"/>
<colgroup span="7"/>
<colgroup span="7"/>

<thead>
   <tr>
      <th colspan="7">January</th>
      <th colspan="7">February</th>
      <th colspan="7">March</th>
   </tr>
</thead>
<tbody>
   <tr>
      <td>S</td><td>M</td><td>T</td><td>W</td><td>T</td><td>F</td><td>S</td>
      <td>S</td><td>M</td><td>T</td><td>W</td><td>T</td><td>F</td><td>S</td>
      <td>S</td><td>M</td><td>T</td><td>W</td><td>T</td><td>F</td><td>S</td>
   </tr>
</tbody>
<tbody>
   <tr>
      <td></td><td></td><td>1</td><td>2</td><td>3</td><td>4</td><td>5</td>
      <td></td><td></td><td></td><td></td><td></td><td>1</td><td>2</td>
      <td></td><td></td><td></td><td></td><td></td><td>1</td><td>2</td>
   </tr>
   <tr>
      <td>6</td><td>7</td><td>8</td><td>9</td><td>10</td><td>11</td><td>12</td>
      <td>3</td><td>4</td><td>5</td><td>6</td><td>7</td><td>8</td><td>9</td>
      <td>3</td><td>4</td><td>5</td><td>6</td><td>7</td><td>8</td><td>9</td>
   </tr>
   <tr>
      <td>13</td><td>14</td><td>15</td><td>16</td><td>17</td><td>18</td><td>19</td>
      <td>10</td><td>11</td><td>12</td><td>13</td><td>14</td><td>15</td><td>16</td>
      <td>10</td><td>11</td><td>12</td><td>13</td><td>14</td><td>15</td><td>16</td>
   </tr>
   <tr>
      <td>20</td><td>21</td><td>22</td><td>23</td><td>24</td><td>25</td><td>26</td>
      <td>17</td><td>18</td><td>19</td><td>20</td><td>21</td><td>22</td><td>23</td>
      <td>17</td><td>18</td><td>19</td><td>20</td><td>21</td><td>22</td><td>23</td>
   </tr>
   <tr>
      <td>27</td><td>28</td><td>29</td><td>30</td><td>31</td><td></td><td></td>
      <td>24</td><td>25</td><td>26</td><td>27</td><td>28</td><td></td><td></td>
      <td>24</td><td>25</td><td>26</td><td>27</td><td>28</td><td>29</td><td>30</td>
   </tr>
   <tr>
      <td></td><td></td><td></td><td></td><td></td><td></td><td></td>
      <td></td><td></td><td></td><td></td><td></td><td></td><td></td>
      <td>31</td><td></td><td></td><td></td><td></td><td></td><td></td>
   </tr>
</tbody>
</table>

                      Calendar for 2002
===================================================================
      January         |       February      |        March  
 S  M  T  W  T  F  S  | S  M  T  W  T  F  S | S  M  T  W  T  F  S 
-------------------------------------------------------------------
       1  2  3  4  5  |                1  2 |                1  2
 6  7  8  9  10 11 12 | 3  4  5  6  7  8  9 | 3  4  5  6  7  8  9
 13 14 15 16 17 18 19 | 10 11 12 13 14 15 16| 10 11 12 13 14 15 16
 20 21 22 23 24 25 26 | 17 18 19 20 21 22 23| 17 18 19 20 21 22 23
 27 28 29 30 31       | 24 25 26 27 28      | 24 25 26 27 28 29 30
                      |                     |                   31
===================================================================

19.5. The tbody element

The tbody element contains rows of table data. In tables that also contain thead or tfoot elements, all of these sections must contain the same number of columns.

19.6. The td and th elements

Table cells may contain two types of information: header information and data. This distinction enables user agents to render header and data cells distinctly, even in the absence of style sheets. For example, visual user agents may present header cell text with a bold font. Speech synthesizers may render header information with a distinct voice inflection.

The th element defines a cell that contains header information. User agents have two pieces of header information available: the contents of the th element and the value of the abbr attribute. User agents must render either the contents of the cell or the value of the abbr attribute. For visual media, the latter may be appropriate when there is insufficient space to render the full contents of the cell. For non-visual media abbr may be used as an abbreviation for table headers when these are rendered along with the contents of the cells to which they apply.

The headers and scope attributes also allow authors to help non-visual user agents process header information. Please consult the section on labeling cells for non-visual user agents for information and examples.

The td element defines a cell that contains data.

Cells may be empty (i.e., contain no data).

<table>

<caption>Cups of coffee consumed by each senator</caption>
<summary>This table charts the number of cups
  of coffee consumed by each senator, the type 
  of coffee (decaf or regular), and whether 
  taken with sugar.</summary>

<tbody>
   <tr>
      <th>Name</th>
      <th>Cups</th>
      <th>Type of Coffee</th>
      <th>Sugar?</th>
   </tr>
   <tr>
      <td>T. Sexton</td>
      <td>10</td>
      <td>Espresso</td>
      <td>No</td>
   </tr>
   <tr>
      <td>J. Dinnen</td>
      <td>5</td>
      <td>Decaf</td>
      <td>Yes</td>
</tbody>
</table>

Name         Cups       Type of Coffee   Sugar?
T. Sexton    10         Espresso         No
J. Dinnen    5          Decaf            Yes

19.6.1. Cells that span several rows or columns

Cells may span several rows or columns. The number of rows or columns spanned by a cell is set by the rowspan and colspan attributes for the th and td elements.

<table>
<caption>Cups of coffee consumed by each senator</caption>
<tbody>
   <tr>
      <th>Name</td>
      <th>Cups</td>
      <th>Type of Coffee</td>
      <th>Sugar?</td>
   </tr>
   <tr>
      <td>T. Sexton</td>
      <td>10</td>
      <td>Espresso</td>
      <td>No</td>
   </tr>
   <tr>
      <td>J. Dinnen</td>
      <td>5</td>
      <td>Decaf</td>
      <td>Yes</td>
   </tr>
   <tr>
      <td>A. Soria</td>
      <td colspan="3"><em>Not available</em></td>
   </tr>
</tbody>
</table>

Cups of coffee consumed by each senator
 --------------------------------------
 |   Name  |Cups|Type of Coffee|Sugar?|
 --------------------------------------
 |T. Sexton|10  |Espresso      |No    |
 --------------------------------------
 |J. Dinnen|5   |Decaf         |Yes   |
 --------------------------------------
 |A. Soria |Not available             |
 --------------------------------------

<table>
<tbody>
   <tr>
      <td>1</td>
      <td rowspan="2">2</td>
      <td>3</td>
   </tr>
   <tr>
      <td>4
      <td>6</td>
   </tr>
   <tr>
      <td>7</td>
      <td>8</td>
      <td>9</td>
      </td></td>
   </tr>
</tbody>
</table>

-------------
| 1 | 2 | 3 | 
----|   |----
| 4 |   | 6 |
----|---|----
| 7 | 8 | 9 |
-------------

<table>
<tbody>
   <tr>
      <td>1</td>
      <td>2</td>
      <td>3</td>
   </tr>
   <tr>
      <td colspan="2">4</td>
      <td>6</td>
   </tr>
   <tr>
      <td>7</td>
      <td>8</td>
      <td>9</td>
   </tr>
</tbody>
</table>

-------------
| 1 | 2 | 3 | 
--------|----
| 4     | 6 |
--------|----
| 7 | 8 | 9 |
-------------

Defining overlapping cells is an error. User agents may vary in how they handle this error (e.g., rendering may vary).

<table">
<tbody>
   <tr>
      <td>1</td>
      <td>2</td>
      <td>3</td>
   </tr>
   <tr>
      <td>4</td>
      <td rowspan="2">5</td>
      <td>6</td>
   </tr>
   <tr>
      <td colspan="2">7</td>
      <td>9</td>
   </tr>
</tbody>
</table>

19.7. The thead and tfoot elements

Table rows may be grouped into a table head, table foot, and one or more table body sections, using the thead , tfoot and tbody elements, respectively. This division enables user agents to support scrolling of table bodies independently of the table head and foot. When long tables are printed, the table head and foot information may be repeated on each page that contains table data.

The table head and table foot should contain information about the table's columns. The table body should contain rows of table data.

When present, each thead , tfoot , and tbody contains a row group . Each row group must contain at least one row, defined by the tr element.

If the thead , tfoot , and tbody elements are used, and a rowspan attriubte is used within a group, the rowspan must remain within the group boundaries of which it is defined.

<table>
<thead>
     <tr> ...header information...</tr>
</thead>
<tfoot>
     <tr> ...footer information...</tr>
</tfoot>
<tbody>
     <tr> ...first row of block one data...</tr>
     <tr> ...second row of block one data...</tr>
</tbody>
<tbody>
     <tr> ...first row of block two data...</tr>
     <tr> ...second row of block two data...</tr>
     <tr> ...third row of block two data...</tr>
</tbody>
</table>

tfoot must appear before tbody within a table definition so that user agents can render the foot before receiving all of the (potentially numerous) rows of data.

19.8. The tr element

The tr elements acts as a container for a row of table cells.

<table>

<caption>Cups of coffee consumed by each senator</caption>
<summary>This table charts the number of cups
  of coffee consumed by each senator, the type 
  of coffee (decaf or regular), and whether 
  taken with sugar.</summary>

<tbody>
   <tr> ...A header row...</tr>
   <tr> ...First row of data...</tr>
   <tr> ...Second row of data...</tr>
   ...the rest of the table...</tr>
</tbody>
</table>

20. XForms Module

This section is informative .

The XForms Module provides a rich collection of forms features. It is defined in [ XFORMS ].

Implementation: XML Schema

21. XML Events Module

This section is informative .

The XML Events Module defines a linkage between XHTML and the XML Document Object Model [ DOM ]. XML Events are defined in [ XMLEVENTS ].

When this module is selected, the listener element is added to the content model of the head element as defined in the Structure Module.

Implementation: RELAX NG , XML Schema , DTD

A. Changes from XHTML 1.1

This appendix is informative .

This Appendix describes the differences between XHTML 2.0 and XHTML 1.1.

B. XHTML 2.0 RELAX NG Definition

This appendix is normative .

This appendix contains the implementation of the XHTML 2.0 RELAX NG driver file.

B.0.1. RELAX NG XHTML 2.0 Driver

<?xml version="1.0" encoding="UTF-8"?>
<grammar ns="http://www.w3.org/2002/06/xhtml2"
         xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>RELAX NG schema for XHTML 2.0</x:h1>
  <x:pre>
    Copyright &#xA9;2003 W3C&#xAE; (MIT, ERCIM, Keio), All Rights Reserved.
      Editor:   Masayasu Ishikawa &lt;mimasa@w3.org&gt;
      Revision: $Id: xhtml2.rng,v 1.25 2003/05/01 05:53:05 mimasa Exp $
    Permission to use, copy, modify and distribute this RELAX NG schema
    for XHTML 2.0 and its accompanying documentation for any purpose and
    without fee is hereby granted in perpetuity, provided that the above
    copyright notice and this paragraph appear in all copies. The copyright
    holders make no representation about the suitability of this RELAX NG
    schema for any purpose.
    It is provided "as is" without expressed or implied warranty.
    For details, please refer to the W3C software license at:
      <x:a href="http://www.w3.org/Consortium/Legal/copyright-software"
      >http://www.w3.org/Consortium/Legal/copyright-software</x:a>
  </x:pre>
  <div>
    <x:h2>XHTML 2.0 modules</x:h2>
    <x:h3>Attribute Collections Module</x:h3>
    <include href="xhtml-attribs-2.rng"/>
    <x:h3>Structure Module</x:h3>
    <include href="xhtml-struct-2.rng"/>
    <x:h3>Block Text Module</x:h3>
    <include href="xhtml-blktext-2.rng"/>
    <x:h3>Inline Text Module</x:h3>
    <include href="xhtml-inltext-2.rng"/>
    <x:h3>Hypertext Module</x:h3>
    <include href="xhtml-hypertext-2.rng"/>
    <x:h3>List Module</x:h3>
    <include href="xhtml-list-2.rng"/>
    <x:h3>Linking Module</x:h3>
    <include href="xhtml-link-2.rng"/>
    <x:h3>Metainformation Module</x:h3>
    <include href="xhtml-meta-2.rng"/>
    <x:h3>Object Module</x:h3>
    <include href="xhtml-object-2.rng"/>
    <x:h3>Scripting Module</x:h3>
    <include href="xhtml-script-2.rng"/>
    <x:h3>Style Attribute Module</x:h3>
    <include href="xhtml-inlstyle-2.rng"/>
    <x:h3>Style Sheet Module</x:h3>
    <include href="xhtml-style-2.rng"/>
    <x:h3>Tables Module</x:h3>
    <include href="xhtml-table-2.rng"/>
    <x:h3>Support Modules</x:h3>
    <x:h4>Datatypes Module</x:h4>
    <include href="xhtml-datatypes-2.rng"/>
    <x:h4>Events Module</x:h4>
    <include href="xhtml-events-2.rng"/>
    <x:h4>Param Module</x:h4>
    <include href="xhtml-param-2.rng"/>
    <x:h4>Caption Module</x:h4>
    <include href="xhtml-caption-2.rng"/>
  </div>
  <div>
    <x:h2>XML Events module</x:h2>
    <include href="xml-events-1.rng"/>
  </div>
  <div>
    <x:h2>Ruby module</x:h2>
    <include href="full-ruby-1.rng"/>
  </div>
  <div>
    <x:h2>XForms module</x:h2>
    <x:p>To-Do: work out integration of XForms</x:p>
    <!--include href="xforms-1.rng"/-->
  </div>
</grammar>

C. XHTML RELAX NG Module Implementations

This appendix is normative .

This appendix contains implementations of the modules defined in this specification. These module implementations can be used in other XHTML Family Document Types.

C.1. XHTML Module Implementations

This section contains the formal definition of each of the XHTML Abstract Modules as a RELAX NG module.

C.1.1. Attribute Collections

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Attribute Collections Module</x:h1>
  <div>
    <x:h2>Core Attribute Collection</x:h2>
    <define name="class.attrib">
      <optional>
        <attribute name="class">
          <ref name="NMTOKENS.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="id.attrib">
      <optional>
        <attribute name="id">
          <ref name="ID.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="title.attrib">
      <optional>
        <attribute name="title">
          <ref name="Text.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="Core.attrib">
      <ref name="id.attrib"/>
      <ref name="class.attrib"/>
      <ref name="title.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>I18N Attribute Collection</x:h2>
    <define name="lang.attrib">
      <optional>
        <attribute name="xml:lang">
          <ref name="LanguageCode.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="I18n.attrib">
      <ref name="lang.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>Bi-directional Text Collection</x:h2>
    <define name="dir.attrib">
      <optional>
        <attribute name="dir">
          <choice>
            <value>ltr</value>
            <value>rtl</value>
            <value>lro</value>
            <value>rlo</value>
          </choice>
        </attribute>
      </optional>
    </define>
    <define name="Bidi.attrib">
      <ref name="dir.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>Edit Collection</x:h2>
    <define name="edit.attrib">
      <optional>
        <attribute name="edit">
          <choice>
            <value>inserted</value>
            <value>deleted</value>
            <value>changed</value>
            <value>moved</value>
          </choice>
        </attribute>
      </optional>
    </define>
    <define name="datetime.attrib">
      <optional>
        <attribute name="datetime">
          <ref name="Datetime.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="Edit.attrib">
      <ref name="edit.attrib"/>
      <ref name="datetime.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>Hypertext Attribute Collection</x:h2>
    <define name="href.attrib">
      <optional>
        <attribute name="href">
          <ref name="URI.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="cite.attrib">
      <optional>
        <attribute name="cite">
          <ref name="URI.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="target.attrib">
      <optional>
        <attribute name="target">
          <ref name="HrefTarget.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="rel.attrib">
      <optional>
        <attribute name="rel">
          <ref name="LinkTypes.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="rev.attrib">
      <optional>
        <attribute name="rev">
          <ref name="LinkTypes.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="accesskey.attrib">
      <optional>
        <attribute name="accesskey">
          <ref name="Character.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="navindex.attrib">
      <optional>
        <attribute name="navindex">
          <ref name="navindexNumber.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="base.attrib">
      <optional>
        <attribute name="xml:base">
          <ref name="URI.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="Hypertext.attrib">
      <ref name="href.attrib"/>
      <ref name="cite.attrib"/>
      <ref name="target.attrib"/>
      <ref name="rel.attrib"/>
      <ref name="rev.attrib"/>
      <ref name="accesskey.attrib"/>
      <ref name="navindex.attrib"/>
      <ref name="base.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>Embedding Attribute Collection</x:h2>
    <define name="src.attrib">
      <optional>
        <attribute name="src">
          <ref name="URI.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="type.attrib">
      <optional>
        <attribute name="type">
          <ref name="ContentType.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="Embedding.attrib">
      <ref name="src.attrib"/>
      <ref name="type.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>Image Map Attribute Collection</x:h2>
    <define name="usemap.attrib">
      <optional>
        <attribute name="usemap">
          <ref name="URI.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="ismap.attrib">
      <optional>
        <attribute name="ismap">
          <value>ismap</value>
        </attribute>
      </optional>
    </define>
    <define name="shape.attrib">
      <optional>
        <attribute name="shape">
          <choice>
            <value>rect</value>
            <value>circle</value>
            <value>poly</value>
            <value>default</value>
          </choice>
        </attribute>
      </optional>
    </define>
    <define name="coords.attrib">
      <optional>
        <attribute name="coords"/>
      </optional>
    </define>
    <define name="ImageMap.attrib">
      <ref name="usemap.attrib"/>
      <ref name="ismap.attrib"/>
      <ref name="shape.attrib"/>
      <ref name="coords.attrib"/>
    </define>
  </div>
  <define name="Common.extra.attrib">
    <empty/>
  </define>
  <define name="Common.attrib">
    <ref name="Core.attrib"/>
    <ref name="I18n.attrib"/>
    <ref name="Bidi.attrib"/>
    <ref name="Edit.attrib"/>
    <ref name="Hypertext.attrib"/>
    <ref name="Embedding.attrib"/>
    <ref name="ImageMap.attrib"/>
    <ref name="Common.extra.attrib"/>
  </define>
  <define name="CommonIdRequired.attrib">
    <attribute name="id">
      <ref name="ID.datatype"/>
    </attribute>
    <ref name="class.attrib"/>
    <ref name="title.attrib"/>
    <ref name="I18n.attrib"/>
    <ref name="Bidi.attrib"/>
    <ref name="Edit.attrib"/>
    <ref name="Hypertext.attrib"/>
    <ref name="Embedding.attrib"/>
    <ref name="ImageMap.attrib"/>
    <ref name="Common.extra.attrib"/>
  </define>
</grammar>

C.1.2. Structure

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Structure Module</x:h1>
  <start>
    <ref name="html"/>
  </start>
  <div>
    <x:h2>The html element</x:h2>
    <define name="html">
      <element name="html">
        <ref name="html.attlist"/>
        <ref name="head"/>
        <ref name="body"/>
      </element>
    </define>
    <define name="html.attlist">
      <ref name="Common.attrib"/>
      <ref name="profile.attlist"/>
    </define>
    <define name="profile.attlist">
      <optional>
        <attribute name="profile">
          <ref name="URIs.datatype"/>
        </attribute>     
      </optional>
    </define>
  </div>
  <div>
    <x:h2>The head element</x:h2>
    <define name="head">
      <element name="head">
        <ref name="head.attlist"/>
        <ref name="head.content"/>
      </element>
    </define>
    <define name="head.attlist">
      <ref name="Common.attrib"/>
    </define>
    <define name="head.content">
      <ref name="title"/>
    </define>
  </div>
  <div>
    <x:h2>The title element</x:h2>
    <define name="title">
      <element name="title">
        <ref name="title.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="title.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The body element</x:h2>
    <define name="body">
      <element name="body">
        <ref name="body.attlist"/>
        <ref name="Block.model"/>
      </element>
    </define>
    <define name="body.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
</grammar>

C.1.3. Block Text

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Block Text Module</x:h1>
  <div>
    <x:h2>The address element</x:h2>
    <define name="address">
      <element name="address">
        <ref name="address.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="address.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The blockcode element</x:h2>
    <define name="blockcode">
      <element name="blockcode">
        <ref name="blockcode.attlist"/>
        <ref name="blockcode.content"/>
      </element>
    </define>
    <define name="blockcode.attlist">
      <ref name="Common.attrib"/>
    </define>
    <define name="blockcode.content">
      <ref name="blockcode.model"/>
    </define>
  </div>
  <div>
    <x:h2>The blockquote element</x:h2>
    <define name="blockquote">
      <element name="blockquote">
        <ref name="blockquote.attlist"/>
        <ref name="blockquote.content"/>
      </element>
    </define>
    <define name="blockquote.attlist">
      <ref name="Common.attrib"/>
    </define>
    <define name="blockquote.content">
      <ref name="blockquote.model"/>
    </define>
  </div>
  <div>
    <x:h2>The div element</x:h2>
    <define name="div">
      <element name="div">
        <ref name="div.attlist"/>
        <ref name="Flow.model"/>
      </element>
    </define>
    <define name="div.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The heading elements</x:h2>
    <define name="h">
      <element name="h">
        <ref name="Heading.attrib"/>
        <ref name="Heading.content"/>
      </element>
    </define>
 
    <define name="h1">
      <element name="h1">
        <ref name="Heading.attrib"/>
        <ref name="Heading.content"/>
      </element>
    </define>
 
    <define name="h2">
      <element name="h2">
        <ref name="Heading.attrib"/>
        <ref name="Heading.content"/>
      </element>
    </define>
     
    <define name="h3">
      <element name="h3">
        <ref name="Heading.attrib"/>
        <ref name="Heading.content"/>
      </element>
    </define>
 
    <define name="h4">
      <element name="h4">
        <ref name="Heading.attrib"/>
        <ref name="Heading.content"/>
      </element>
    </define>
 
    <define name="h5">
      <element name="h5">
        <ref name="Heading.attrib"/>
        <ref name="Heading.content"/>
      </element>
    </define>
    <define name="h6">
      <element name="h6">
        <ref name="Heading.attrib"/>
        <ref name="Heading.content"/>
      </element>
    </define>
    <define name="Heading.attrib">
      <ref name="Common.attrib"/>
    </define>
 
    <define name="Heading.content">
      <ref name="Inline.model"/>
    </define>
  </div>
  <div>
    <x:h2>The hr element</x:h2>
    <define name="hr">
      <element name="hr">
        <ref name="hr.attlist"/>
      </element>
    </define>
    <define name="hr.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The p element</x:h2>
    <define name="p">
      <element name="p">
        <ref name="p.attlist"/>
        <ref name="p.content"/>
      </element>
    </define>
    <define name="p.attlist">
      <ref name="Common.attrib"/>
    </define>
    <define name="p.content">
      <ref name="p.model"/>
    </define>
  </div>
  <div>
    <x:h2>The pre element</x:h2>
    <define name="pre">
      <element name="pre">
        <ref name="pre.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="pre.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The section element</x:h2>
    <define name="section">
      <element name="section">
        <ref name="section.attlist"/>
        <ref name="Flow.model"/>
      </element>
    </define>
    <define name="section.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>Content Model</x:h2>
    <define name="Heading.class">
      <choice>
        <ref name="h"/>
        <ref name="h1"/>
        <ref name="h2"/>
        <ref name="h3"/>
        <ref name="h4"/>
        <ref name="h5"/>
        <ref name="h6"/>
      </choice>
    </define>
    <define name="Block.class">
      <choice>
        <ref name="address"/>
        <ref name="blockcode"/>
        <ref name="blockquote"/>
        <ref name="div"/>
        <ref name="hr"/>
        <ref name="p"/>
        <ref name="pre"/>
        <ref name="section"/>
      </choice>
    </define>
    <define name="blockcode.model">
      <zeroOrMore>
        <choice>
          <text/>
          <ref name="Inline.class"/>
          <ref name="Heading.class"/>
          <ref name="Block.class"/>
          <ref name="List.class"/>
          <ref name="Misc.class"/>
        </choice>
      </zeroOrMore>
    </define>
    <define name="blockquote.model">
      <zeroOrMore>
        <choice>
          <text/>
          <ref name="Inline.class"/>
          <ref name="Heading.class"/>
          <ref name="Block.class"/>
          <ref name="List.class"/>
          <ref name="Misc.class"/>
        </choice>
      </zeroOrMore>
    </define>
    <define name="p.model">
      <zeroOrMore>
        <choice>
          <text/>
          <ref name="Inline.class"/>
          <ref name="List.class"/>
          <ref name="blockquote"/>
          <ref name="pre"/>
          <ref name="table"/>
          <ref name="Misc.class"/>
        </choice>
      </zeroOrMore>
    </define>
    <define name="Block.mix">
      <zeroOrMore>
        <choice>
          <ref name="Heading.class"/>
          <ref name="Block.class"/>
          <ref name="List.class"/>
          <ref name="Misc.class"/>
        </choice>
      </zeroOrMore>
    </define>
    <define name="Block.model">
      <oneOrMore>
        <ref name="Block.mix"/>
      </oneOrMore>
    </define>
    <define name="Flow.model">
      <zeroOrMore>
        <choice>
          <text/>
          <ref name="Heading.class"/>
          <ref name="Block.class"/>
          <ref name="List.class"/>
          <ref name="Inline.class"/>
          <ref name="Misc.class"/>
        </choice>
      </zeroOrMore>
    </define>
  </div>
</grammar>

C.1.4. Inline Text

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Inline Text Module</x:h1>
  <div>
    <x:h2>The abbr element</x:h2>
    <define name="abbr">
      <element name="abbr">
        <ref name="abbr.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="abbr.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The cite element</x:h2>
    <define name="cite">
      <element name="cite">
        <ref name="cite.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="cite.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The code element</x:h2>
    <define name="code">
      <element name="code">
        <ref name="code.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="code.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The dfn element</x:h2>
    <define name="dfn">
      <element name="dfn">
        <ref name="dfn.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="dfn.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The em element</x:h2>
    <define name="em">
      <element name="em">
        <ref name="em.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="em.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The kbd element</x:h2>
    <define name="kbd">
      <element name="kbd">
        <ref name="kbd.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="kbd.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The l element</x:h2>
    <define name="l">
      <element name="l">
        <ref name="l.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="l.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The quote element</x:h2>
    <define name="quote">
      <element name="quote">
        <ref name="quote.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="quote.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The samp element</x:h2>
    <define name="samp">
      <element name="samp">
        <ref name="samp.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="samp.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The span element</x:h2>
    <define name="span">
      <element name="span">
        <ref name="span.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="span.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The strong element</x:h2>
    <define name="strong">
      <element name="strong">
        <ref name="strong.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="strong.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The sub element</x:h2>
    <define name="sub">
      <element name="sub">
        <ref name="sub.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="sub.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The sup element</x:h2>
    <define name="sup">
      <element name="sup">
        <ref name="sup.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="sup.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The var element</x:h2>
    <define name="var">
      <element name="var">
        <ref name="var.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="var.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:p>these can occur at block or inline level</x:p>
    <define name="Misc.class">
      <empty/>
    </define>
  </div>
  <div>
    <x:h2>Content Model</x:h2>
    <define name="Inline.class">
      <choice>
        <ref name="abbr"/>
        <ref name="cite"/>
        <ref name="code"/>
        <ref name="dfn"/>
        <ref name="em"/>
        <ref name="kbd"/>
        <ref name="l"/>
        <ref name="quote"/>
        <ref name="samp"/>
        <ref name="span"/>
        <ref name="strong"/>
        <ref name="sub"/>
        <ref name="sup"/>
        <ref name="var"/>
      </choice>
    </define>
    <define name="Inline.model">
      <zeroOrMore>
        <choice>
          <text/>
          <ref name="Inline.class"/>
          <ref name="Misc.class"/>
        </choice>
      </zeroOrMore>
    </define>
  </div>
</grammar>

C.1.5. Hypertext

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Hypertext Module</x:h1>
  <div>
    <x:h2>The a element</x:h2>
    <define name="a">
      <element name="a">
        <ref name="a.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="a.attlist">
      <ref name="Common.attrib"/>
      <optional>
        <attribute name="charset">
          <ref name="Charset.datatype"/>
        </attribute>
      </optional>
    </define>
  </div>
  <define name="Inline.class" combine="choice">
    <ref name="a"/>
  </define>
</grammar>

C.1.6. List

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>List Module</x:h1>
  <div>
    <x:h2>The dl element</x:h2>
    <define name="dl">
      <element name="dl">
        <ref name="dl.attlist"/>
        <oneOrMore>
          <choice>
        <ref name="dt"/>
        <ref name="dd"/>
          </choice>
        </oneOrMore>
      </element>
    </define>
    <define name="dl.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The dt element</x:h2>
    <define name="dt">
      <element name="dt">
        <ref name="dt.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="dt.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The dd element</x:h2>
    <define name="dd">
      <element name="dd">
        <ref name="dd.attlist"/>
        <ref name="Flow.model"/>
      </element>
    </define>
    <define name="dd.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The label element</x:h2>
    <define name="label">
      <element name="label">
        <ref name="label.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="label.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The nl element</x:h2>
    <define name="nl">
      <element name="nl">
        <ref name="nl.attlist"/>
        <ref name="label"/>
        <oneOrMore>
          <ref name="li"/>
        </oneOrMore>
      </element>
    </define>
    <define name="nl.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The ol element</x:h2>
    <define name="ol">
      <element name="ol">
        <ref name="ol.attlist"/>
        <oneOrMore>
          <ref name="li"/>
        </oneOrMore>
      </element>
    </define>
    <define name="ol.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The ul element</x:h2>
    <define name="ul">
      <element name="ul">
        <ref name="ul.attlist"/>
        <oneOrMore>
          <ref name="li"/>
        </oneOrMore>
      </element>
    </define>
    <define name="ul.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The li element</x:h2>
    <define name="li">
      <element name="li">
        <ref name="li.attlist"/>
        <ref name="Flow.model"/>
      </element>
    </define>  
    <define name="li.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>List Content Set</x:h2>
    <define name="List.class">
      <choice>
        <ref name="ul"/>
        <ref name="nl"/>
        <ref name="ol"/>
        <ref name="dl"/>
      </choice>
    </define>
  </div>
</grammar>

C.1.7. Link

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Link Module</x:h1>
  <div>
    <x:h2>The link element</x:h2>
    <define name="link">
      <element name="link">
        <ref name="link.attlist"/>
      </element>
    </define>
    <define name="link.attlist">
      <ref name="Common.attrib"/>
      <optional>
        <attribute name="charset">
          <ref name="Charset.datatype"/>
        </attribute>
      </optional>
      <optional>
        <attribute name="media">
          <ref name="MediaDesc.datatype"/>
        </attribute>
      </optional>
    </define>
  </div>
  <define name="head.content" combine="interleave">
    <zeroOrMore>
      <ref name="link"/>
    </zeroOrMore>
  </define>
</grammar>

C.1.8. Metainformation

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Metainformation Module</x:h1>
  <div>
    <x:h2>The meta element</x:h2>
    <define name="meta">
      <element name="meta">
        <ref name="meta.attlist"/>
        <choice>
          <ref name="Inline.model"/>
          <oneOrMore>
            <ref name="meta"/>
          </oneOrMore>
        </choice>
      </element>
    </define>
    <define name="meta.attlist">
      <ref name="Common.attrib"/>
      <optional>
        <attribute name="name">
          <ref name="NMTOKEN.datatype"/>
        </attribute>
      </optional>
    </define>
  </div>
  <define name="head.content" combine="interleave">
    <zeroOrMore>
      <ref name="meta"/>
    </zeroOrMore>
  </define>
</grammar>

C.1.9. Object

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Object Module</x:h1>
  <div>
    <x:h2>The object element</x:h2>
    <define name="object">
      <element name="object">
        <ref name="object.attlist"/>
        <optional>
          <ref name="caption"/>
        </optional>
        <optional>
          <ref name="standby"/>
        </optional>
        <zeroOrMore>
          <ref name="param"/>
        </zeroOrMore>
        <ref name="Flow.model"/>
      </element>
    </define>
    <define name="object.attlist">
      <ref name="Common.attrib"/>
      <optional>
        <attribute name="archive">
          <ref name="URIs.datatype"/>
        </attribute>
      </optional>
      <optional>
        <attribute name="content-length">
          <ref name="Number.datatype"/>
        </attribute>
      </optional>
      <optional>
        <attribute name="data">
          <ref name="URI.datatype"/>
        </attribute>
      </optional>
      <optional>
        <attribute name="declare">
          <value>declare</value>
        </attribute>
      </optional>
    </define>
  </div>
  <div>
    <x:h2>The standby element</x:h2>
    <define name="standby">
      <element name="standby">
        <ref name="standby.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="standby.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <define name="Inline.class" combine="choice">
    <ref name="object"/>
  </define>
</grammar>

C.1.10. Scripting

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Scripting Module</x:h1>
  <div>
    <x:h2>The noscript element</x:h2>
    <define name="noscript">
      <element name="noscript">
        <ref name="noscript.attlist"/>
        <ref name="Block.model"/>
      </element>
    </define>
    <define name="noscript.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The script element</x:h2>
    <define name="script">
      <element name="script">
        <ref name="script.attlist"/>
        <choice>
          <text/>
          <ref name="script"/>
          <ref name="noscript"/>
        </choice>
      </element>
    </define>
    <define name="script.attlist">
      <optional>
        <attribute name="charset">
          <ref name="Charset.datatype"/>
        </attribute>
      </optional>
      <optional>
        <attribute name="declare">
          <value>declare</value>
        </attribute>
      </optional>
      <optional>
        <attribute name="src">
          <ref name="URI.datatype"/>
        </attribute>
      </optional>
      <attribute name="type">
        <ref name="ContentType.datatype"/>
      </attribute>
      <optional>
        <attribute name="xml:space">
          <value>preserve</value>
        </attribute>
      </optional>
    </define>
  </div>
  <define name="head.content" combine="interleave">
    <zeroOrMore>
      <ref name="script"/>
    </zeroOrMore>
  </define>
  <define name="Script.class">
    <choice>
      <ref name="noscript"/>
      <ref name="script"/>
    </choice>
  </define>
  <define name="Inline.class" combine="choice">
    <ref name="Script.class"/>
  </define>
  <define name="Block.class" combine="choice">
    <ref name="Script.class"/>
  </define>
</grammar>

C.1.11. Style Attribute

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Style Attribute Module</x:h1>
  <define name="style.attrib">
    <optional>
      <attribute name="style"/>
    </optional>
  </define>
  <define name="Common.extra.attrib" combine="interleave">
    <ref name="style.attrib"/>
  </define>
</grammar>

C.1.12. Style Sheet

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Style Module</x:h1>
  <div>
    <x:h2>The style element</x:h2>
    <define name="style">
      <element name="style">
        <ref name="style.attlist"/>
        <text/>
      </element>
    </define>
    <define name="style.attlist">
      <ref name="Common.attrib"/>
      <optional>
        <attribute name="media">
          <ref name="MediaDesc.datatype"/>
        </attribute>
      </optional>
    </define>
  </div>
  <define name="head.content" combine="interleave">
    <zeroOrMore>
      <ref name="style"/>
    </zeroOrMore>
  </define>
</grammar>

C.1.13. Tables

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Tables Module</x:h1>
  <x:p>Note. Also include the Caption Module when this module is used.</x:p>
  <div>
    <x:h2>The table element</x:h2>
    <define name="table">
      <element name="table">
        <ref name="table.attlist"/>
        <optional>
          <ref name="caption"/>
        </optional>
        <optional>
          <ref name="summary"/>
        </optional>
        <choice>
          <zeroOrMore>
            <ref name="col"/>
          </zeroOrMore>
          <zeroOrMore>
            <ref name="colgroup"/>
          </zeroOrMore>
        </choice>
        <choice>
          <group>
            <optional>
              <ref name="thead"/>
            </optional>
            <optional>
              <ref name="tfoot"/>
            </optional>
            <oneOrMore>
              <ref name="tbody"/>
            </oneOrMore>
          </group>
          <oneOrMore>
            <ref name="tr"/>
          </oneOrMore>
        </choice>
      </element>
    </define>
    <define name="table.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The summary element</x:h2>
    <define name="summary">
      <element name="summary">
        <ref name="summary.attlist"/>
        <ref name="Flow.model"/>
      </element>
    </define>
    <define name="summary.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The col element</x:h2>
    <define name="col">
      <element name="col">
        <ref name="col.attlist"/>
      </element>
    </define>
    <define name="col.attlist">
      <ref name="Common.attrib"/>
      <ref name="span.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The colgroup element</x:h2>
    <define name="colgroup">
      <element name="colgroup">
        <ref name="colgroup.attlist"/>
        <zeroOrMore>
          <ref name="col"/>
        </zeroOrMore>
      </element>
    </define>
    <define name="colgroup.attlist">
      <ref name="Common.attrib"/>
      <ref name="span.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The thead element</x:h2>
    <define name="thead">
      <element name="thead">
        <ref name="thead.attlist"/>
        <oneOrMore>
          <ref name="tr"/>
        </oneOrMore>
      </element>
    </define>
    <define name="thead.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The tfoot element</x:h2>
    <define name="tfoot">
      <element name="tfoot">
        <ref name="tfoot.attlist"/>
        <oneOrMore>
          <ref name="tr"/>
        </oneOrMore>
      </element>
    </define>
    <define name="tfoot.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The tbody element</x:h2>
    <define name="tbody">
      <element name="tbody">
        <ref name="tbody.attlist"/>
        <oneOrMore>
          <ref name="tr"/>
        </oneOrMore>
      </element>
    </define>
    <define name="tbody.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The tr element</x:h2>
    <define name="tr">
      <element name="tr">
        <ref name="tr.attlist"/>
        <oneOrMore>
          <choice>
            <ref name="th"/>
            <ref name="td"/>
          </choice>
        </oneOrMore>
      </element>
    </define>
    <define name="tr.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The th element</x:h2>
    <define name="th">
      <element name="th">
        <ref name="th.attlist"/>
        <ref name="Flow.model"/>
      </element>
    </define>
    <define name="th.attlist">
      <ref name="Cell.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>The td element</x:h2>
    <define name="td">
      <element name="td">
        <ref name="td.attlist"/>
        <ref name="Flow.model"/>
      </element>
    </define>
    <define name="td.attlist">
      <ref name="Cell.attrib"/>
    </define>
  </div>
  <div>
    <x:h2>Attribute definitions</x:h2>
    <define name="span.attrib">
      <optional>
        <attribute name="span" a:defaultValue="1">
          <ref name="spanNumber.datatype"/>
        </attribute>
      </optional>
    </define>
    <define name="Cell.attrib">
      <ref name="Common.attrib"/>
      <optional>
        <attribute name="abbr">
          <ref name="Text.datatype"/>
        </attribute>
      </optional>
      <optional>
        <attribute name="axis"/>
      </optional>
      <optional>
        <attribute name="colspan" a:defaultValue="1">
          <ref name="Number.datatype"/>
        </attribute>
      </optional>
      <optional>
        <attribute name="headers">
          <ref name="IDREFS.datatype"/>
        </attribute>
      </optional>
      <optional>
        <attribute name="rowspan" a:defaultValue="1">
          <ref name="Number.datatype"/>
        </attribute>
      </optional>
      <ref name="scope.attrib"/>
    </define>
    <define name="scope.attrib">
      <optional>
        <attribute name="scope">
          <choice>
            <value>row</value>
            <value>col</value>
            <value>rowgroup</value>
            <value>colgroup</value>
          </choice>
        </attribute>
      </optional>
    </define>
  </div>
  <define name="Block.class" combine="choice">
    <ref name="table"/>
  </define>
</grammar>

C.2. XHTML RELAX NG Support Modules

The modules in this section are elements and attributes of the XHTML RELAX NG implementation that, while hidden from casual users, are important to understand when creating derivative markup languages using the Modularization architecture.

C.2.1. Datatypes

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml"
         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
  <x:h1>Datatypes Module</x:h1>
  <div>
    <x:h2>Datatypes defined in XML 1.0</x:h2>
    <define name="CDATA.datatype">
      <text/>
    </define>
    <define name="ID.datatype">
      <data type="ID"/>
    </define>
    <define name="IDREF.datatype">
      <data type="IDREF"/>
    </define>
    <define name="IDREFS.datatype">
      <data type="IDREFS"/>
    </define>
    <define name="NAME.datatype">
      <data type="Name"/>
    </define>
    <define name="NMTOKEN.datatype">
      <data type="NMTOKEN"/>
    </define>
    <define name="NMTOKENS.datatype">
      <data type="NMTOKENS"/>
    </define>
  </div>
  <div>
    <x:h2>Additional Datatypes</x:h2>
    <define name="Character.datatype">
      <x:p>A single character, as per section 2.2 of [XML].</x:p>
      <data type="string">
        <param name="length">1</param>
      </data>
    </define>
    <define name="Charset.datatype">
      <x:p>A character encoding, as per [RFC2045].</x:p>
      <text/>
    </define>
    <define name="Charsets.datatype">
      <x:p>A space separated list of character encodings,
        as per [RFC2045].</x:p>
      <list>
        <oneOrMore>
          <ref name="Charset.datatype"/>
        </oneOrMore>
      </list>
    </define>
    <define name="ContentType.datatype">
      <x:p>A list of media ranges with optional accept parameters,
        as defined in section 14.1 of [RFC2616] as the field value
        of the accept request header.</x:p>
      <text/>
    </define>
    <define name="Coordinates.datatype">
      <x:p>Comma separated list of Lengths used in defining areas.</x:p>
      <data type="string">
        <param name="pattern">[\-+]?(\d+|\d+(\.\d+)?%)(,\s*[\-+]?(\d+|\d+(\.\d+)?%))*</param>
      </data>
    </define>
    <define name="Datetime.datatype">
      <x:p>Date and time information, as defined by the type dateTime
        in [XMLSCHEMA].</x:p>
      <data type="dateTime"/>
    </define>
    <define name="HrefTarget.datatype">
      <x:p>Name used as destination for results of certain actions.</x:p>
      <ref name="NMTOKEN.datatype"/>
    </define>
    <define name="LanguageCode.datatype">
      <x:p>A language code, as per [RFC3066].</x:p>
      <data type="language"/>
    </define>
    <define name="Length.datatype">
      <x:p>The value may be either in pixels or a percentage of the available
        horizontal or vertical space. Thus, the value "50%" means half of
        the available space.</x:p>
      <data type="string">
        <param name="pattern">[\-+]?(\d+|\d+(\.\d+)?%)</param>
      </data>
    </define>
    <define name="LinkTypes.datatype">
      <x:p>Space-separated list of link types.</x:p>
      <ref name="NMTOKENS.datatype"/>
    </define>
    <define name="MediaDesc.datatype">
      <x:p>A comma-separated list of media descriptors as described by [CSS].
        The default is all.</x:p>
      <data type="string">
        <param name="pattern">[^,]+(,\s*[^,]+)*</param>
      </data>
    </define>
    <define name="Number.datatype">
      <x:p>One or more digits (NUMBER).</x:p>
      <data type="nonNegativeInteger">
        <param name="pattern">[0-9]+</param>
      </data>
    </define>
    <define name="spanNumber.datatype">
      <x:p>span: this attribute value must be an integer > 0;
        the default value is 1.</x:p>
      <data type="positiveInteger">
        <param name="pattern">[0-9]+</param>
      </data>
    </define>
    <define name="navindexNumber.datatype">
      <x:p>navindex: the position of the current element in the navingation
        order for the current document. This value must be a number between
        0 and 32767. User agents must ignore leading zeros.</x:p>
      <data type="nonNegativeInteger">
        <param name="pattern">[0-9]+</param>
        <param name="minInclusive">0</param>
        <param name="maxInclusive">32767</param>
      </data>
    </define>
    <define name="Shape.datatype">
      <x:p>The shape of a region.</x:p>
      <choice>
        <value>rect</value>
        <value>circle</value>
        <value>poly</value>
        <value>default</value>
      </choice>
    </define>
    <define name="Text.datatype">
      <x:p>Arbitrary textual data, likely meant to be human-readable.</x:p>
      <text/>
    </define>
    <define name="URI.datatype">
      <x:p>A Uniform Resource Identifier Reference, as defined by the type
        anyURI in [XMLSCHEMA].</x:p>
      <data type="anyURI"/>
    </define>
    <define name="URIs.datatype">
      <x:p>A space-separated list of URIs as defined above.</x:p>
      <list>
        <oneOrMore>
          <data type="anyURI"/>
        </oneOrMore>
      </list>
    </define>
    <define name="URIList.datatype">
      <x:p>A comma-separated list of URIs as defined above.</x:p>
      <text/>
    </define>
  </div>
</grammar>

C.2.2. Events

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:ev="http://www.w3.org/2001/xml-events"
         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Events Attribute Collection Module</x:h1>
  <define name="Events.attrib">
    <optional>
      <attribute name="ev:event">
        <ref name="NMTOKEN.datatype"/>
      </attribute>
    </optional>
    <optional>
      <attribute name="ev:observer">
        <ref name="IDREF.datatype"/>
      </attribute>
    </optional>
    <optional>
      <attribute name="ev:target">
        <ref name="IDREF.datatype"/>
      </attribute>
    </optional>
    <optional>
      <attribute name="ev:handler">
        <ref name="URI.datatype"/>
      </attribute>
    </optional>
    <optional>
      <attribute name="ev:phase" a:defaultValue="default">
        <choice>
          <value>capture</value>
          <value>default</value>
        </choice>
      </attribute>
    </optional>
    <optional>
      <attribute name="ev:propagate" a:defaultValue="continue">
        <choice>
          <value>stop</value>
          <value>continue</value>
        </choice>
      </attribute>
    </optional>
    <optional>
      <attribute name="ev:defaultAction" a:defaultValue="perform">
        <choice>
          <value>cancel</value>
          <value>perform</value>
        </choice>
      </attribute>
    </optional>
  </define>
  <define name="Common.extra.attrib" combine="interleave">
    <ref name="Events.attrib"/>
  </define>
  <define name="head.content" combine="interleave">
    <zeroOrMore>
      <ref name="listener" ns="http://www.w3.org/2001/xml-events"/>
    </zeroOrMore>
  </define>
  <define name="Script.class" combine="choice">
    <ref name="listener" ns="http://www.w3.org/2001/xml-events"/>
  </define>
</grammar>

C.2.3. Param

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Param Module</x:h1>
  <div>
    <x:h2>The param element</x:h2>
    <define name="param">
      <element name="param">
        <ref name="param.attlist"/>
      </element>
    </define>
    <define name="param.attlist">
      <optional>
        <ref name="id.attrib"/>
      </optional>
      <attribute name="name"/>
      <optional>
        <attribute name="value"/>
      </optional>
      <optional>
        <attribute name="valuetype" a:defaultValue="data">
          <choice>
            <value>data</value>
            <value>ref</value>
            <value>object</value>
          </choice>
        </attribute>
      </optional>
    </define>
  </div>
</grammar>

C.2.4. Caption

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Caption Module</x:h1>
  <div>
    <x:h2>The caption element</x:h2>
    <define name="caption">
      <element name="caption">
        <ref name="caption.attlist"/>
        <ref name="Inline.model"/>
      </element>
    </define>
    <define name="caption.attlist">
      <ref name="Common.attrib"/>
    </define>
  </div>
</grammar>

C.3. RELAX NG External Modules

These modules are not defined by XHTML, but these definitions are included here for completeness.

C.3.1. Ruby

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml"
         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
  <x:h1>Ruby Module in RELAX NG</x:h1>
  <x:pre>
    Ruby Elements
      ruby, rbc, rtc, rb, rt, rp
    This module defines grammars to support ruby annotation markup.
    This module is based on the W3C Ruby Annotation Specification:
      http://www.w3.org/TR/ruby
    Copyright &#xA9;2003 W3C&#xAE; (MIT, ERCIM, Keio), All Rights Reserved.
      Editor:   Masayasu Ishikawa &lt;mimasa@w3.org&gt;
      Revision: $Id: ruby-1.rng,v 1.7 2003/05/01 04:58:15 mimasa Exp $
    Permission to use, copy, modify and distribute this RELAX NG schema
    for Ruby Annotation and its accompanying documentation for any purpose
    and without fee is hereby granted in perpetuity, provided that the above
    copyright notice and this paragraph appear in all copies. The copyright
    holders make no representation about the suitability of this RELAX NG
    schema for any purpose.
    It is provided "as is" without expressed or implied warranty.
    For details, please refer to the W3C software license at:
      <x:a href="http://www.w3.org/Consortium/Legal/copyright-software"
      >http://www.w3.org/Consortium/Legal/copyright-software</x:a>
  </x:pre>
  <div>
    <x:h2>patterns for the content model of the ruby element</x:h2>
    <define name="Ruby.content.simple">
      <x:p>Content model of simple ruby</x:p>
      <group>
        <ref name="rb"/>
        <choice>
          <ref name="rt-simple"/>
          <group>
            <ref name="rp"/>
            <ref name="rt-simple"/>
            <ref name="rp"/>
          </group>
        </choice>
      </group>
    </define>
    <define name="Ruby.content.complex">
      <x:p>Content model of complex ruby</x:p>
      <group>
        <ref name="rbc"/>
        <ref name="rtc"/>
        <optional>
          <ref name="rtc"/>
        </optional>
      </group>
    </define>
    <define name="Ruby.content">
      <x:p>Simple ruby is used by default</x:p>
      <ref name="Ruby.content.simple"/>
    </define>
  </div>
  <div>
    <x:h2>Ruby Elements</x:h2>
    <x:h3>ruby element</x:h3>
    <define name="ruby">
      <element name="ruby">
        <ref name="Ruby.content"/>
        <ref name="Ruby.common.attrib"/>
      </element>
    </define>
    <x:h3>rbc (ruby base component) element</x:h3>
    <define name="rbc">
      <element name="rbc">
        <oneOrMore>
          <ref name="rb"/>
        </oneOrMore>
        <ref name="Ruby.common.attrib"/>
      </element>
    </define>
    <x:h3>rtc (ruby text component) element</x:h3>
    <define name="rtc">
      <element name="rtc">
        <oneOrMore>
          <ref name="rt-complex"/>
        </oneOrMore>
        <ref name="Ruby.common.attrib"/>
      </element>
    </define>
    <x:h3>rb (ruby base) element</x:h3>
    <define name="rb">
      <element name="rb">
        <ref name="NoRuby.content"/>
        <ref name="Ruby.common.attrib"/>
      </element>
    </define>
    <x:h3>rt (ruby text) element</x:h3>
    <define name="rt-simple">
      <x:p>grammar for simple ruby</x:p>
      <x:p>rbspan attribute is not allowed in simple ruby</x:p>
      <element name="rt">
        <ref name="NoRuby.content"/>
        <ref name="Ruby.common.attrib"/>
      </element>
    </define>
    <define name="rt-complex">
      <x:p>grammar for complex ruby</x:p>
      <element name="rt">
        <ref name="NoRuby.content"/>
        <ref name="Ruby.common.attrib"/>
        <optional>
          <attribute name="rbspan" a:defaultValue="1">
            <data type="positiveInteger">
              <param name="pattern">[1-9][0-9]*</param>
            </data>
          </attribute>
        </optional>
      </element>
    </define>
    <x:h3>rp (ruby parenthesis) element</x:h3>
    <define name="rp">
      <element name="rp">
        <text/>
        <ref name="Ruby.common.attrib"/>
      </element>
    </define>
  </div>
  <div>
    <x:h2>Ruby Common Attributes</x:h2>
    <x:p>Ruby elements are intended to have common attributes of its
      parent markup language. The pattern "Common.attrib" MUST be
      defined to integrate this module.</x:p>
    <define name="Ruby.common.attrib">
      <ref name="Common.attrib"/>
    </define>
  </div>
  <div>
    <x:p>Content models of the rb and the rt elements are intended to
      allow other inline-level elements of its parent markup language,
      but it should not include ruby descendent elements. This RELAX NG
      module itself doesn't check nesting of ruby elements.
      The patterns "Inline.class" and "Inline.model" MUST be defined
      to integrate this module.</x:p>
    <define name="Inline.class" combine="choice">
      <ref name="ruby"/>
    </define>
    <define name="NoRuby.content">
      <ref name="Inline.model"/>
    </define>
  </div>
</grammar>

C.3.2. Ruby Driver for Full Ruby Markup

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml">
  <x:h1>Ruby Module in RELAX NG for full ruby markup</x:h1>
  <x:pre>
    Copyright &#xA9;2003 W3C&#xAE; (MIT, ERCIM, Keio), All Rights Reserved.
      Editor:   Masayasu Ishikawa &lt;mimasa@w3.org&gt;
      Revision: $Id: full-ruby-1.rng,v 1.4 2003/04/30 06:50:03 mimasa Exp $
  </x:pre>
  <include href="ruby-1.rng"/>
  <define name="Ruby.content" combine="choice">
    <x:p>Allow complex ruby markup in addition to simple ruby markup</x:p>
    <ref name="Ruby.content.complex"/>
  </define>
</grammar>

C.3.3. XML Events

<?xml version="1.0" encoding="UTF-8"?>
<grammar ns="http://www.w3.org/2001/xml-events"
         xmlns="http://relaxng.org/ns/structure/1.0"
         xmlns:ev="http://www.w3.org/2001/xml-events"
         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
         xmlns:x="http://www.w3.org/1999/xhtml"
         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
  <x:h1>XML Events Module in RELAX NG</x:h1>
  <x:pre>
    Copyright &#xA9;2003 W3C&#xAE; (MIT, ERCIM, Keio), All Rights Reserved.
      Editor:   Masayasu Ishikawa &lt;mimasa@w3.org&gt;
      Revision: $Id: xml-events-1.rng,v 1.6 2003/04/30 06:50:03 mimasa Exp $
    Permission to use, copy, modify and distribute this RELAX NG schema
    for XML Events and its accompanying documentation for any purpose and
    without fee is hereby granted in perpetuity, provided that the above
    copyright notice and this paragraph appear in all copies. The copyright
    holders make no representation about the suitability of this RELAX NG
    schema for any purpose.
    It is provided "as is" without expressed or implied warranty.
    For details, please refer to the W3C software license at:
      <x:a href="http://www.w3.org/Consortium/Legal/copyright-software"
      >http://www.w3.org/Consortium/Legal/copyright-software</x:a>
  </x:pre>
  <define name="listener">
    <element name="listener">
      <ref name="listener.attlist"/>
    </element>
  </define>
  <define name="listener.attlist">
    <optional>
      <attribute name="event">
        <data type="NMTOKEN"/>
      </attribute>
    </optional>
    <optional>
      <attribute name="observer">
        <data type="IDREF"/>
      </attribute>
    </optional>
    <optional>
      <attribute name="target">
        <data type="IDREF"/>
      </attribute>
    </optional>
    <optional>
      <attribute name="handler">
        <data type="anyURI"/>
      </attribute>
    </optional>
    <optional>
      <attribute name="phase" a:defaultValue="default">
        <choice>
          <value>capture</value>
          <value>default</value>
        </choice>
      </attribute>
    </optional>
    <optional>
      <attribute name="propagate" a:defaultValue="continue">
        <choice>
          <value>stop</value>
          <value>continue</value>
        </choice>
      </attribute>
    </optional>
    <optional>
      <attribute name="defaultAction" a:defaultValue="perform">
        <choice>
          <value>cancel</value>
          <value>perform</value>
        </choice>
      </attribute>
    </optional>
    <optional>
      <attribute name="id">
        <data type="ID"/>
      </attribute>
    </optional>
  </define>
</grammar>

D. XHTML 2.0 Schema

This appendix is normative .

This appendix will contain the implementation of the XHTML 2.0 Schema driver file and content model file.

E. XHTML Schema Module Implementations

This appendix is normative .

This appendix will contain implementations of the modules defined in this specification via XML Schema [ XMLSCHEMA ] when XML Schema becomes a W3C Recommendation.

F. XHTML 2.0 Document Type Definition

This appendix is normative .

This appendix will contain the implementation of the XHTML 2.0 DTD driver file and content model file.

G. XHTML DTD Module Implementations

This appendix is normative .

This appendix will contain implementations of the modules defined in this specification. These module implementations can be used in other XHTML Family Document Types.

G.1. XHTML Modular Framework

In order to take advantage of the XHTML DTD Modules, DTD authors need to define the content model for their DTD. XHTML provides a variety of tools to ease this effort. They are defined in a set of support modules, instantiated by a main Framework module:

Module DTD/xhtml-framework-2.mod not found!

Note that the module above references a content model module. This module is defined on a per-document type basis in addition to the document type driver file. The Modular framework also relies upon the following component modules:

G.1.1. XHTML Base Architecture

G.1.2. XHTML Notations

G.1.3. XHTML Datatypes

G.1.4. XHTML Common Attribute Definitions

G.1.5. XHTML Qualified Names

G.1.6. XHTML Character Entities

G.2. XHTML Module Implementations

This section contains the formal definition of each of the XHTML Abstract Modules as a DTD module.

G.2.1. Structure

G.2.2. Block Text

G.2.3. Inline Text

G.2.4. Hypertext

G.2.5. List

G.2.6. Link

G.2.7. Metainformation

G.2.8. Object

G.2.9. Scripting

G.2.10. Style Attribute

G.2.11. Style Sheet

G.2.12. Tables

G.3. XHTML DTD Support Modules

The modules in this section are elements of the XHTML DTD implementation that, while hidden from casual users, are important to understand when creating derivative markup languages using the Modularization architecture.

G.3.1. Param

H. List of Elements

This appendix is informative .

This appendix will contain a list of elements defined in this specification, sorted in alphabetical order, with some other relevant information and links to the element definitions.

J. List of Attributes

This appendix is informative .

This appendix will contain a list of attributes defined in this specification, sorted in alphabetical order, with some other relevant information and links to the attribute definitions.

I. Cross-reference Index

This appendix is informative .

This appendix will contain a detailed index of this document, with links to the indexed terms.

K. References

This appendix is normative .

K.1. Normative References

[CSS2]

" Cascading Style Sheets, level 2 (CSS2) Specification ", W3C Recommendation, B. Bos et al. , eds. , 12 May 1998.
Available at: http://www.w3.org/TR/1998/REC-CSS2-19980512

[DOM]

" Document Object Model (DOM) Level 2 Core Specification ", W3C Recommendation, A. Le Hors et al. , eds. , 13 November 2000.
Available at: http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113
A list of DOM Level 2 specifications can be found at: http://www.w3.org/DOM/DOMTR#dom2

[MIMETYPES]

List of registered content types (MIME media types). Download a list of registered content types from http://www.iana.org/assignments/media-types/ .

[P3P]

" The Platform for Privacy Preferences 1.0 (P3P1.0) Specification ", W3C Recommendation, L. Cranor et al. , 16 April 2002.
Available at: http://www.w3.org/TR/2002/REC-P3P-20020416/

[RELAXNG]

" RELAX NG Specification ", OASIS Committee Specification, J. Clark, Murata M., eds. , 3 December 2001.
Available at: http://relaxng.org/spec-20011203.html
RELAX NG is being standardized as part of ISO / IEC 19757 - Document Schema Definition Languages ( DSDL ), currently a Final Draft International Standard ( FDIS ). See home page for Document Schema Definition Languages at http://dsdl.org/ for details.

[RFC2045]

" Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies ", RFC 2045, N. Freed and N. Borenstein, November 1996.
Available at: http://www.rfc-editor.org/rfc/rfc2045.txt

[RFC2119]

" Key words for use in RFCs to indicate requirement levels ", RFC 2119, S. Bradner, March 1997.
Available at: http://www.rfc-editor.org/rfc/rfc2119.txt

[RFC2616]

" Hypertext Transfer Protocol -- HTTP/1.1 ", RFC 2616, R. Fielding et al. , June 1999.
Available at: http://www.rfc-editor.org/rfc/rfc2616.txt

[RFC3066]

" Tags for the Identification of Languages ", RFC 3066, H. Alvestrand, January 2001.
Available at: http://www.rfc-editor.org/rfc/rfc3066.txt

[RUBY]

" Ruby Annotation ", W3C Recommendation, M. Sawicki et al. , eds. , 31 May 2001.
Available at: http://www.w3.org/TR/2001/REC-ruby-20010531

[SGML]

" Information Processing -- Text and Office Systems -- Standard Generalized Markup Language (SGML) ", ISO 8879:1986.
Please consult the ISO Web site at http://www.iso.ch/ for information about the standard, or http://www.oasis-open.org/cover/general.html#overview about SGML.

[UAX9]

" Unicode Standard Annex #9: The Bidirectional Algorithm ", M. Davis, 17 April 2003.
Available at: http://www.unicode.org/reports/tr9/tr9-11.html
The latest version of UAX #9 is available at: http://www.unicode.org/reports/tr9/

[URI]

" Uniform Resource Identifiers (URI): Generic Syntax ", RFC 2396, T. Berners-Lee et al. , August 1998.
Available at: http://www.rfc-editor.org/rfc/rfc2396.txt.

[XFORMS]

" XForms 1.0 ", W3C Candidate Recommendation, M. Dubinko et al. , eds. , 12 November 2002, work in progress .
Available at: http://www.w3.org/TR/2002/CR-xforms-20021112/

[XHTMLMOD]

" Modularization of XHTML ", W3C Recommendation, M. Altheim et al. , eds. , 10 April 2001
Available at: http://www.w3.org/TR/2001/REC-xhtml-modularization-20010410

[XML]

" Extensible Markup Language (XML) 1.0 (Second Edition) ", W3C Recommendation, T. Bray et al. , eds. , 6 October 2000.
Available at: http://www.w3.org/TR/2000/REC-xml-20001006

[XMLBASE]

" XML Base ", W3C Recommendation, J. Marsh, ed. , 27 June 2001.
Available at: http://www.w3.org/TR/2001/REC-xmlbase-20010627/

[XMLEVENTS]

" XML Events ", W3C Candidate Recommendation, S. McCarron et al. , eds. , 7 February 2003, work in progress .
Available at: http://www.w3.org/TR/2003/CR-xml-events-20030207

[XMLNAMES]

" Namespaces in XML ", W3C Recommendation, T. Bray et al. , eds. , 14 January 1999.
Available at: http://www.w3.org/TR/1999/REC-xml-names-19990114

[XMLSCHEMA]

" XML Schema Part 1: Structures ", W3C Recommendation, H. S. Thompson et al. , eds. , 2 May 2001.
Available at: http://www.w3.org/TR/2001/REC-xmlschema-1-20010502
See also " XML Schema Part 2: Datatypes ", available at: http://www.w3.org/TR/2001/REC-xmlschema-2-20010502

K.2. Informative References

[HTML4]

" HTML 4.01 Specification ", W3C Recommendation, D. Raggett et al. ,eds. ,24 December 1999.
Available at: http://www.w3.org/TR/1999/REC-html401-19991224

[XFRAMES]

" XFrames ", W3C Working Draft, S. Pemberton, ed. , 6 August 2002, work in progress .
Available at: http://www.w3.org/TR/2002/WD-xframes-20020806

[XLINK]

" XML Linking Language (XLink) Version 1.0 ", W3C Recommendation, S. DeRose et al. , eds. , 27 June 2001.
Available at: http://www.w3.org/TR/2001/REC-xlink-20010627/

L. Acknowledgements

This appendix is informative .

This specification was prepared by the W3C HTML Working Group. The participants at the time of publication were:

This section will be updated at publication time.