XHTML™ 2.0

W3C Working Draft 5 August 2002

This version:

http://www.w3.org/TR/2002/WD-xhtml2-20020805

Latest version:

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

Editors:

Shane McCarron, Applied Testing and Technology

Jonny Axelsson, Opera Software

Beth Epperson, Netscape/AOL

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 ©2002 W3C^® (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply.

Abstract

This Working Draft specifies the XHTML 2.0 Markup Language and a variety of XHTML-conforming modules that support that language.

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 first public working draft of this specification. It should in no way be considered stable, and should not be referenced for any purposes whatsoever. This version does not include the implementations of XHTML 2.0 in either DTD or XML Schema form. Those will be included in subsequent versions, once the contents of this language stabilizes.

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 zero 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 markup language intended for rich, portable web-based applications. While the ancestry of XHTML 2 comes from HTML 4, XHTML 1.0, and XHTML 1.1, it is not intended to be backward compatible with its earlier versions. Application developers familiar with earlier its ancestors will be comfortable working with XHTML 2. Appendix A describes the ways in which XHTML 2 differs from previous versions and what application developers need to know to convert existing applications to XHTML 2.

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, 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 parse-able 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 Schema or Appendix D - 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 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 C using its Formal Public Identifier. The system identifier may be modified appropriately.

   <!DOCTYPE
    html PUBLIC "-//W3C//DTD XHTML 2.0//EN"
    "http://www.w3.org/TR/xhtml2/DTD/xhtml2.dtd">
   

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"
    "http://www.w3.org/TR/xhtml2/DTD/xhtml2.dtd">
<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

Text Module*

abbr, acronym, address, blockquote, br, cite, code, dfn, div, em, h, h1, h2, h3, h4, h5, h6, kbd, line, p, pre, quote, samp, section, span, strong, var

Hypertext Module*

a

List Module*

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

Bidirectional Text Module

bdo

Client-side Image Map Module

area, map

Edit Module

del, ins

Link Module

link

Metainformation Module

meta

Object Module

object, param

Presentation Module

hr, sub, sup

Scripting Module

noscript, script

Server-side Image Map Module

Attribute ismap on img

Stylesheet Module

style element

Target Module

target attribute

Table Module

caption, col, colgroup, 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]

LOTS OF ELEMENTS

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

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 = ClassName

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

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

id = ID

The id attribute assigns a 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 rendered 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.

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

Example:

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

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 http://www.w3.org/TR/REC-xml#sec-lang-tag. 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"
   "http://www.w3.org/xhtml2/DTD/xhtml2.dtd">
<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. Hypertext Attribute Collection

href = URI

This attribute specifies a hypertext link that is activated when the element is selected.

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 evaluated in.

XFrames not published yet

We need a reference to XFrames here, but XFrames is not yet public.

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 an access key to a link defined by the a element. Typing this access key takes the user to another document, in this case, a table of contents.

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

navindex = Number

This attribute specifies 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.

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 must 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.
3. Elements that are disabled do not participate in the navigation order.

Tabbing keys. The actual key sequence that causes navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key is used for navigation and the "enter" key is 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).

6.4. 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 the default action to take when the matching event is encountered. If not specified, the defaultAction is perform

event = CDATA

This attribute defines the name of the event that is to be captured. 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.

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 down the event chain for possible further processing. If not specified, 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. Instead, they are in the XML Events namespace. The XHTML namespace is the default namespace for XHTML documents, so XHTML elements and attributes do not require namespace prefixes (although they are permitted). XML Events attributes MUST use a prefix, since they are not in the default namespace of the document. When XML Events are included in an XHTML document, the default prefix for those attribute is ev.

6.5. Common Attribute Collection

This collection assembles the Core, I18N, Events 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: DTD

7.1. The html element

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

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. User agents do not generally render elements that appear in the head as content. They may, however, make information in the head available to users through other mechanisms.

7.3. The title element

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

Authors should use the title element to identify the contents of a document. Since users often consult documents 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 (including title elements that occur in frames). The mechanism for doing so depends on the user agent (e.g., as a caption, spoken).

Titles may contain entity references (for accented characters, special characters, etc.), but may not contain other markup (including comments). Here is a sample document title:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 2.0//EN"
   "http://www.w3.org/TR/xhtml2/DTD/xhtml2.dtd">
<html xmlns="http://www.w3.org/2002/06/xhtml2">
<head>
<title>A study of population dynamics</title>
... other head elements...
</head>
<body>
... document body...
</body>
</html>

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 Text Module

This section is normative.

This module defines all of the basic text container elements, attributes, and their content model:

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

Heading

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

Block

address | blockquote | div | p | pre

Inline

abbr | acronym | br | cite | code | dfn | em | kbd | q | samp | span | strong | var

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 (in other words, a style sheet might give an element within the Block content a display property of inline).

Implementation: DTD

8.1. The abbr element

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

The content of the abbr and acronym elements 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 and acronyms 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>

8.2. The acronym element

The acronym element indicates that a text fragment is an acronym (e.g., BBC, WWW, URL, etc.). Its usage is the same as the abbr element above.

While some dictionaries define an acronym to be just a word formed from the initial letters of other words, others require the acronym to be pronouncable as a word. This specification does not require the acronym element to adhere to either definition, but is only provided for author convenience.

  <acronym title="World Wide Web">WWW</acronym>
  <acronym xml:lang="fr" 
        title="Société Nationale des Chemins de Fer">
     SNCF
  </acronym>

8.3. 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>
<a href="mailto:webmaster@example.net">Webmaster</a>
</address>

8.4. 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>

8.5. The br element

The br element indicates that the current output line should be ended at this point, and a new line begun. This element is deprecated in favor of the line element.

<p class="poem" xml:lang="fr">
Un petit d'un petit<br/>
S'etonne aux Halles.<br/>
Un petit d'un petit,<br/>
Ah! Degres te fallent.
</p>

8.6. 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 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>.

8.7. The code element

The code element contains a fragment of computer code.

The <code>code</code> element contains a fragment of computer code.

8.8. 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.

8.9. The div element

The div element, in conjunction with the id and class attributes, offer a generic mechanism for adding 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>

8.10. The em element

The em element indicates emphasis for its contents.

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

8.11. 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 indicate the importance of the heading.

<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 */

8.12. The kbd element

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

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

8.13. The line element

The line element represents a sub-paragraph. It is intended as a structured replacement for the br element. It contains a piece of text that when visually represented should start on a new line, and have a line break at the end. Whether the line should wrap or not visually depends on styling properties of the element.

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

.program { counter-reset: linenumber }

line:before {
    position: relative;
    left: -1em;
    counter-increment: linenumber;
    content: counter(linenumber);
}

8.14. 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.

Authors are discouraged from using empty p elements. User agents should ignore empty p.

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

8.15. The pre element

The pre element indicates that whitespace in the enclosed text has semantic relevance, and will normally be included in 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 all elements may preserve or collapse whitespace on rendering, under control of a stylesheet. Also note that there is no 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.

8.16. The quote element

This element designates a inline text fragment of quoted text.

Visual user agents are not required to add delimiting quotation marks (as was the case for the q element in earlier versions of HTML). It is the responsibility of the document author to add any required quotation marks.

<p>John said, <quote lang="en-us">"I saw Lucy at lunch, she told me
<quote lang="en-us">'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.w3.org/Public/www-html/June2002/001.html">We quite agree</quote>

8.17. The samp element

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

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

8.18. 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>    

8.19. 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>

8.20. The strong element

The strong element indicates strong emphasis for its contents.

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

8.21. 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.

9. XHTML Hypertext Module

This section is normative.

The Hypertext Module provides the element that is used to define hypertext links to other resources, as well as a number of attributes.

This module supports the following element:

This module adds the a element to the Inline content set of the Text Module, and activates the Hypertext Attribute Collection.

Implementation: DTD

9.1. The a element

Each a element defines an anchor.

1. The a element's content defines the position of the anchor.
2. The href attribute makes this anchor the source anchor of exactly one link.

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.
                                                   ~~~~~~~~~~~~

For more information about W3C, please consult the 
<a href="http://www.w3.org/" charset="ISO-8859-1">W3C Web site</a> 

...text before the anchor...
<a name="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>.

10. 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 Text Module.

Implementation: DTD

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. We discourage authors from using lists purely as a means of indenting text. This is a stylistic issue and is properly handled by style sheets.

10.1. 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.

10.2. 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 name element that defines the name for the list.

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

1. The contents of the name element are presented.
2. When the name 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 name'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>
   <name>Contents </name>
   <li href="#introduction">Introduction</li>
   <li>
      <nl>
          <name>Terms</name>
          <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>

10.3. 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>

10.4. 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.

10.5. The name element

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

11. XHTML Bi-directional Text Module

This section is normative.

The Bi-directional Text module defines an element that can be used to declare the bi-directional rules for the element's content.

When this module is used, the bdo element is added to the Inline content set of the Text Module. Selecting this module also adds the attribute dir* ("ltr" | "rtl") to the I18N attribute collection.

Implementation: DTD

11.1. The bdo element

The bidirectional algorithm and the dir attribute generally suffice to manage embedded direction changes. However, some situations may arise when the bidirectional algorithm results in incorrect presentation. The bdo element allows authors to turn off the bidirectional algorithm for selected fragments of text.

english1 HEBREW2 english3 HEBREW4 english5 HEBREW6

english1 2WERBEH english3
4WERBEH english5 6WERBEH

<pre>
<bdo dir="ltr">english1 2WERBEH english3</bdo>
<bdo dir="ltr">4WERBEH english5 6WERBEH</bdo>
</pre>

english1 2WERBEH english3
4WERBEH english5 6WERBEH

The bdo element should be used in scenarios where absolute control over sequence order is required (e.g., multi-language part numbers). The dir attribute is mandatory for this element.

Authors may also use special Unicode characters to override the bidirectional algorithm -- LEFT-TO-RIGHT OVERRIDE (202D) or RIGHT-TO-LEFT OVERRIDE (hexadecimal 202E). The POP DIRECTIONAL FORMATTING (hexadecimal 202C) character ends either bidirectional override.

11.1.1. Character references for directionality and joining control

Since ambiguities sometimes arise as to the directionality of certain characters (e.g., punctuation), the [UNICODE] specification includes characters to enable their proper resolution. Also, Unicode includes some characters to control joining behavior where this is necessary (e.g., some situations with Arabic letters). XHTML includes character references for these characters.

The following DTD excerpt presents some of the directional entities:

   <!ENTITY zwnj CDATA "&#8204;"--=zero width non-joiner-->
   <!ENTITY zwj  CDATA "&#8205;"--=zero width joiner-->
   <!ENTITY lrm  CDATA "&#8206;"--=left-to-right mark-->
   <!ENTITY rlm  CDATA "&#8207;"--=right-to-left mark-->

The zwnj entity is used to block joining behavior in contexts where joining will occur but shouldn't. The zwj entity does the opposite; it forces joining when it wouldn't occur but should. For example, the Arabic letter "HEH" is used to abbreviate "Hijri", the name of the Islamic calendar system. Since the isolated form of "HEH" looks like the digit five as employed in Arabic script (based on Indic digits), in order to prevent confusing "HEH" as a final digit five in a year, the initial form of "HEH" is used. However, there is no following context (i.e., a joining letter) to which the "HEH" can join. The zwj character provides that context.

Similarly, in Persian texts, there are cases where a letter that normally would join a subsequent letter in a cursive connection should not. The character zwnj is used to block joining in such cases.

The other characters, lrm and rlm, are used to force directionality of directionally neutral characters. For example, if a double quotation mark comes between an Arabic (right-to-left) and a Latin (left-to-right) letter, the direction of the quotation mark is not clear (is it quoting the Arabic text or the Latin text?). The lrm and rlm characters have a directional property but no width and no word/line break property. Please consult [UNICODE] for more details.

11.1.2. 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.

12. XHTML Client-Side Image Map Module

This section is normative.

The Client-side Image Map Module provides elements for client side image maps. It requires that the Image Module (or another module that supports the img element) be included. The Client-side Image Map Module supports the following elements:

When this module is used, the map element is added to the Inline content set of the Text Module.

Implementation: DTD

12.1. The area element

The area element defines a geometric region associated with an image map, and optionally associates that region with events or external references.

12.2. The map element

The map element specifies a client-side image map (or other navigation mechanism) that may be associated with another object. An image map is associated with an element via the element's usemap attribute. The map element may be used without an associated image for general navigation mechanisms.

The presence of the usemap attribute for an object implies that the object being included is an image. Furthermore , when the object element has an associated client-side image map, user agents may implement user interaction with the object solely in terms of the client-side image map. This allows user agents (such as an audio browser or robot) to interact with the object without having to process it; the user agent may even elect not to retrieve (or process) the object. When an object has an associated image map, authors should not expect that the object will be retrieved or processed by every user agent.

The map element content model allows authors to combine the following:

1. One or more area elements. These elements have no content but specify the geometric regions of the image map and the link associated with each region. Note that user agents do not generally render area elements. Therefore, authors must provide alternate text for each area with the alt attribute.
2. Block-level content. This content should include a elements that specify the geometric regions of the image map and the link associated with each region. Note that the user agent should render block-level content of a map element. Authors should use this method to create more accessible documents.

When a map element contains mixed content (both area elements and block-level content), user agents must ignore the area elements.

Authors should specify an image maps's geometry completely with area elements, or completely with a elements, or completely with both if content is mixed. Authors may wish to mix content so that older user agents will handle map geometries specified by area elements and new user agents will take advantage of richer block content.

If two or more defined regions overlap, the region-defining element that appears earliest in the document takes precedence (i.e., responds to user input).

User agents and authors should offer textual alternates to graphical image maps for cases when graphics are not available or the user cannot access them. For example, user agents may use alt text to create textual links in place of a graphical image map. Such links may be activated in a variety of ways (keyboard, voice activation, etc.).

12.2.1. Client-side image map examples

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

 <html>
   <head>
      <title>The cool site!</title>
   </head> <body>
     <P><object data="navbar1.gif" type="image/gif"
     usemap="#map1"> </object>

     ...the rest of the page here...

     <map name="map1">
       <P>Navigate the site: <A href="guide.html"
       shape="rect" coords="0,0,118,28">Access
       Guide</a> | <A href="shortcut.html" shape="rect"
       coords="118,0,184,28">Go</A> | <A href="search.html"
       shape="circle" coords="184,200,60">Search</A>
       | <A href="top10.html" shape="poly"
       coords="276,0,276,28,100,200,50,50,276,0">Top Ten</A>
     </map>
   </body>
</html> 

 <p><object data="navbar1.gif" type="image/gif"
usemap="#map1">
   <p>This is a navigation bar.  </object>

<map name="map1">
 <area href="guide.html"
          alt="Access Guide" shape="rect" coords="0,0,118,28">
 <area href="search.html"
          alt="Search" shape="rect" coords="184,0,276,28">
 <area href="shortcut.html"
          alt="Go" shape="circle" coords="184,200,60">
 <area href="top10.html"
          alt="Top Ten" shape="poly"
          coords="276,0,276,28,100,200,50,50,276,0">
</map> 

 <p> <object data="navbar.png" type="image/png">
  <object data="navbar.gif" type="image/gif">
    text describing the image...
  </object>
</object> 

 <P> <object data="navbar.png" type="image/png"
usemap="#map1">
  <object data="navbar.gif" type="image/gif" usemap="#map1">
     <map name="map1"> <p>Navigate the site:
      <a href="guide.html" shape="rect" coords="0,0,118,28">Access
      Guide</a> | <a href="shortcut.html" shape="rect"
      coords="118,0,184,28">Go</a> | <a href="search.html"
      shape="circle" coords="184,200,60">Search</a>
      | <a href="top10.html" shape="poly"
      coords="276,0,276,28,100,200,50,50,276,0">Top Ten</a>
     </map>
  </object>
</object> 

 <map name="map1"> <p> <A shape="circle"
coords="100,200,50">I'm inactive.</A> <A
href="outer-ring-link.html" shape="circle" coords="100,200,250">I'm
active.</A> </map> 

Similarly, the nohref attribute for the area element declares that geometric region has no associated link.

13. XHTML Edit Module

This section is normative.

This module defines elements and attributes for use in editing-related markup:

When this module is used, the del and ins elements are added to the Inline content set of the Text Module.

Implementation: DTD

13.1. The del element

The del element is used to indicate that a section of a document has been deleted with respect to a different version of the document (e.g., in draft legislation where lawmakers need to view the changes).

This element is unusual for XHTML in that they may serve as either block-level or inline elements (but not both). It may contain one or more words within a paragraph or contain one or more block-level elements such as paragraphs, lists and tables.

<p>
  A Sheriff can employ <del>3</del><ins>5</ins> deputies.
</p>

The del element must not contain block-level content when it is behaving as an inline element.

<p>
<ins><div>...block-level content...</div></ins>
</p>

User agents should render deleted text in ways that make the change obvious. For instance, inserted text may appear in a special font, deleted text may not be shown at all or be shown as struck-through or with special markings, etc.

     2001-11-05T13:15:30Z
     2001-11-05T08:15:30-05:00

<ins datetime="2001-11-05T08:15:30-05:00"
        cite="http://www.example.org/mydoc/comments.html">
Furthermore, the latest figures from the marketing department
suggest that such practice is on the rise.
</ins>

Authors may also make comments about deleted text by means of the title attribute for the del element. User agents may present this information to the user (e.g., as a popup note). For example:

<del datetime="2001-11-05T08:15:30-05:00"
        title="Changed as a result of Steve G's comments in meeting.">
Furthermore, the latest figures from the marketing department
suggest that such practice is on the rise.
</del>

13.2. The ins element

The ins element is used to indicate that a section of a document has been inserted with respect to a different version of the document (e.g., in draft legislation where lawmakers need to view the changes).

This element is unusual for XHTML in that they may serve as either block-level or inline elements (but not both). It may contain one or more words within a paragraph or contain one or more block-level elements such as paragraphs, lists and tables.

The ins element must not contain block-level content when it is behaving as an inline element.

<p>
<ins><div>...block-level content...</div></ins>
</p>

User agents should render inserted text in ways that make the change obvious. For instance, inserted text may appear in a special font.

     2001-11-05T13:15:30Z
     2001-11-05T08:15:30-05:00

<ins datetime="2001-11-05T08:15:30-05:00"
        cite="http://www.foo.org/mydoc/comments.html">
Furthermore, the latest figures from the marketing department
suggest that such practice is on the rise.
</ins>

Authors may also make comments about inserted text by means of the title attribute for the ins element. User agents may present this information to the user (e.g., as a popup note). For example:

<ins datetime="2001-11-05T08:15:30-05:00"
        title="Changed as a result of Steve B's comments in meeting.">
Furthermore, the latest figures from the marketing department
suggest that such practice is on the rise.
</ins>

14. 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: DTD

14.1. 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>

14.1.1. 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="foo"/>

Has exactly the same meaning as:

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

Both the rel and rev attributes may be specified simultaneously.

14.1.2. 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.

14.1.3. 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"
      type="text/html"
      rel="alternate"
      hreflang="nl" 
      href="http://someplace.com/manual/dutch.html"/>
<link title="The manual in Portuguese"
      type="text/html"
      rel="alternate"
      hreflang="pt" 
      href="http://someplace.com/manual/portuguese.html"/>
<link title="The manual in Arabic"
      type="text/html"
      rel="alternate"
      charset="ISO-8859-6"
      hreflang="ar" 
      href="http://someplace.com/manual/arabic.html"/>
<link lang="fr" title="La documentation en Fran&ccedil;ais"
      type="text/html"
      rel="alternate"
      hreflang="fr"
      href="http://someplace.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://someplace.com/manual/postscript.ps"/>
</head>

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

15. 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: DTD

15.1. 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 attribute specifies the property's value.

<meta name="Author" content="Dave Raggett"/>

The xml:lang attribute can be used with meta to specify the language for the value of the content attribute. This enables speech synthesizers to apply language dependent pronunciation rules.

<meta name="Author" lang="fr" content="Arnaud Le Hors"/>

<meta name="DC.identifier"
      content="http://www.ietf.org/rfc/rfc1866.txt"/>

<link rel="DC.identifier"
         type="text/plain"
         href="http://www.ietf.org/rfc/rfc1866.txt"/>

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

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.

15.1.2. meta and PICS

The Platform for Internet Content Selection (PICS, specified in [PICS]) is an infrastructure for associating labels (meta data) with Internet content. Originally designed to help parents and teachers control what children can access on the Internet, it also facilitates other uses for labels, including code signing, privacy, and intellectual property rights management.

<head>
 <meta http-equiv="PICS-Label" content='
 (PICS-1.1 "http://www.gcf.org/v2.5"
    labels on "1994.11.05T08:15-0500"
      until "1995.12.31T23:59-0000"
      for "http://w3.org/PICS/Overview.html"
    ratings (suds 0.5 density 0 color/hue 1))
 '/>
  <title>... document title ...</title>
</head>

15.1.3. 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 HTML 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 HTML document). This specification does not define formats for profiles.

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

16. 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 Text Module.

Implementation: DTD

16.1. The object element

Most user agents have built-in mechanisms for processing common data types such as text, GIF images, colors, fonts, and a handful of graphic elements. To process data types they don't support natively, user agents generally run external applications. The object element allows authors to control whether data should be processed externally or by some program, specified by the author, that processes the data within the user agent.

In the most general case, an author may need to specify three types of information:

• The implementation of the included object. For instance, if the included object is a clock applet, the author must indicate the location of the applet's executable code.
• The data to be processed. For instance, if the included object is a program that processes font data, the author must indicate the location of that data.
• Additional values required by the object at run-time. For example, some applets may require initial values for parameters.

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

Authors specify an object's implementation 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 elements in the head do 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.

This document does not specify the behavior of object elements that use both the classid attribute to identify an implementation and the data attribute to specify data for that implementation. In order to ensure portability, authors should use the param element to tell implementations where to retrieve additional data.

16.1.1. 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. It should not process the element's contents, but it must examine them in case the element contains any direct children that are param elements (see object initialization) or map elements (see client-side image maps).
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.

    
<object classid="http://www.miamachina.it/analogclock.py">
</object>

    
<p><object classid="http://www.miamachina.it/analogclock.py">
An animated clock.
</object>

One significant consequence of the object element's design is that it offers a mechanism for specifying alternate object processing; each embedded object declaration may specify alternate content types. If a user agent cannot process the outermost object, it tries to process the contents, which may be another object element, etc.

<p>                 <!-- First, try the Python applet -->
<object title="The Earth as seen from space" 
        classid="http://www.observer.mars/TheEarth.py">
                    <!-- Else, try the MPEG video -->
  <object data="TheEarth.mpeg" type="application/mpeg">
                    <!-- Else, try the GIF image -->
    <object data="TheEarth.gif" type="image/gif">
                    <!-- Else render the text -->
     The <strong>Earth</strong> as seen from space.
    </object>
  </object>
</object>

<p>
<object id="clock1"
        classid="clsid:663C8FEF-1EF9-11CF-A3DB-080036F12502"
        data="data:application/x-oleobject;base64, ...base64 data...">
    A clock.
</object>

16.2. The param element.

param elements specify a set of values that may be required by an object 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.

The syntax of names and values is assumed to be understood by the object's implementation. This document does not specify how user agents should retrieve name/value pairs nor how they should interpret parameter names that appear twice.

    
<p><object classid="http://www.miamachina.it/analogclock.py">
<param name="height" value="40" valuetype="data" />
<param name="width" value="40" valuetype="data" />
This user agent cannot render Python applications.
</object>

<p><object classid="http://www.gifstuff.com/gifappli"
       standby="Loading Elvis...">
<param name="Init_values"
       value="./images/elvis.gif"
       valuetype="ref" />
</object>
</p>

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

<p>
<object id="obj1">
   <param name="param1">
   <object id="obj2">
      <param name="param2">
   </object>
</object>

16.2.1. Global naming schemes for objects

The location of an object's implementation is given by a URI. The first segment of an absolute URI specifies the naming scheme used to transfer the data designated by the URI. For XHTML documents, this scheme is frequently "http". Some applets might employ other naming schemes. For instance, when specifying a Java applet, authors may use URIs that begin with "java" and for ActiveX applets, authors may use "clsid".

<p><object classid="java:program.start">
</object>

By setting the codetype attribute, a user agent can decide whether to retrieve the Java application based on its ability to do so.

<object codetype="application/java-archive"
        classid="java:program.start">
</object>

Some rendering schemes require additional information to identify their implementation and must be told where to find that information. Authors may give path information to the object's implementation via the codebase attribute.

<object codetype="application/java-archive"
        classid="java:program.start">
        codebase="http://foooo.bar.com/java/myimplementation/"
</object>

<p><object classid="clsid:663C8FEF-1EF9-11CF-A3DB-080036F12502"
        data="http://www.acme.com/ole/clock.stm">
This application is not supported.
</object>

16.2.2. Object declarations and instantiations

The preceding examples have only illustrated isolated object definitions. When a document is to contain more than one instance of the same object, it is possible to separate the declaration of the object from its instantiations. Doing so has several advantages:

• Data may be retrieved from the network by the user agent one time (during the declaration) and reused for each instantiation.
• It is possible to instantiate an object from a location other than the object's declaration, for example, from a link.
• It is possible to specify objects as run-time data for other objects.

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

A declared object must appear in a document before the first instance of that object.

An object defined with the declare attribute is instantiated every time an element that refers to that object requires it to be rendered (e.g., a link that refers to it is activated, an object that refers to it is activated, etc.).

<p><object declare
        id="earth.declaration" 
        data="TheEarth.mpeg" 
        type="application/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><object declare
     id="tribune"
     type="application/x-webfont"
     data="tribune.gif">
</object>
...view the poem in KublaKhan.txt here...
<p><object classid="http://foo.bar.com/poem_viewer" 
           data="KublaKhan.txt">
<param name="font" valuetype="object" value="#tribune">
<p>You're missing a really cool poem viewer ...
</object>

User agents that don't support the declare attribute must render the contents of the object declaration.

17. XHTML Presentation Module

This section is normative.

This module defines elements, attributes, and a minimal content model for simple presentation-related markup:

When this module is used, the hr element is added to the Block content set of the Text Module. In addition, the sub and sup elements are added to the Inline content set of the Text Module.

Implementation: DTD

17.1. The hr element

The hr element places a horizontal line in the document.

17.2. The sub element

The sub element indicates that its contents should be presented as a subscript of the text baseline.

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 lang="fr">M<sup>lle</sup> Dupont</span>

17.3. The sup element

The sup element indicates that its contents should be presented as a super-script of the text baseline.

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 lang="fr">M<sup>lle</sup> Dupont</span>

18. 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 Text Module. In addition, the script element is added to the content model of the head element defined in the Structure Module.

Implementation: DTD

18.1. The noscript element

The noscript element allows authors to provide alternate content when a script is not executed. The content of a noscript element should only be rendered by a script-aware user agent 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">
 ...some Tcl script to insert data...
</script>
<noscript>
 <p>Access the <a href="http://someplace.com/data">data.</a></p>
</noscript>

18.2. 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.

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

The syntax of script data depends on the scripting language.

18.2.1. 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.

18.2.2. 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/vbscript" src="http://someplace.com/progs/vbcalc"/>
</head>
<body>
<script type="text/javascript">
...some JavaScript...
</script>
</body>
</html>

18.2.3. References to XHTML elements from a script

Each scripting language has its own conventions for referring to XHTML objects from within a script. This specification does not define a standard mechanism for referring to XHTML objects.

18.2.4. Dynamic modification of documents

Scripts that are executed when a document is loaded may be able to modify the document's contents dynamically. The ability to do so depends on the scripting language itself (e.g., the "document.write" statement in the XHTML object model supported by some vendors).

The dynamic modification of a document may be modeled as follows:

1. All script elements are evaluated in order as the document is loaded.
2. All script constructs within a given script element that generate CDATA are evaluated. Their combined generated text is inserted in the document directly after the script element.
3. The generated CDATA is re-evaluated.

XHTML documents are constrained to conform to the XHTML DTD both before and after processing any script elements.

 ...
 <title>Test Document</title>
 ...
 <script type="text/javascript">
     document.write("<p><b>Hello World!<\/b><\/p>")
 </script>
 ...

 ...
 <title>Test Document</title>
 ...
 <p><b>Hello World!</b></p>
 ...

19. XHTML Server-Side Image Map Module

This section is normative.

The Server-side Image Map Module provides support for image-selection and transmission of selection coordinates. It requires that the Object Module (or another module that supports the object element) be included. The Server-side Image Map Module supports the following attributes:

Implementation: DTD

ismap = "ismap"

This attribute indicates that the associated element 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.

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

<p><a href="http://www.example.com/cgi-bin/competition">
        <object src="game.gif" ismap="ismap" alt="target" /></a></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 a element, by appending `?' followed by the x and y coordinates, separated by a comma. The link is then followed 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/competition?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.

20. 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: DTD

20.1. 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>

<head>
 <style type="text/css">
   h1.myclass {border-width: thin; border-style: solid; text-align: center}
 </style>
</head>
<body>
 <h1 class="myclass"> This h1 is affected by our style </h1>
 <h1> This one is not affected by our style </h1>
</body>

<head>
 <style type="text/css">
   #myid {border-width: thin; border-style: solid; text-align: center}
 </style>
</head>
<body>
 <h1 class="myclass"> This h1 is not affected </h1>
 <h1 id="myid"> This h1 is affected by style </h1>
 <h1> This h1 is not affected </h1>
</body>

Although style information may be set for almost every XHTML element, two elements, div and span, are particularly useful in that they do not impose any presentation semantics (besides block-level vs. inline). When combined with style sheets, these elements allow users to extend XHTML indefinitely, particularly when used with the class and id attributes.

<head>
 <style type="text/css">
  span.sc-ex { font-variant: small-caps }
 </style>
</head>
<body>
  <p><span class="sc-ex">The first</span> few words of
  this paragraph are in small-caps.</p>
</body>

<head>
 <style type="text/css">
   div.Abstract { text-align: justify }
 </style>
</head>
<body>
 <div class="Abstract">
   <p>The Chieftain product range is our market winner for
     the coming year. This report sets out how to position
     Chieftain against competing products.</p>

   <p>Chieftain replaces the Commander range, which will
     remain on the price list until further notice.</p>
 </div>
</body>

20.1.1. 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 descriptions).

20.1.2. 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.

20.1.3. 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.

21. XHTML Tables Module

This section is normative.

As its name suggests, the Tables Module provides table-related elements that are updated to enable access by non-visual user agents. Specifically, the Tables 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 Text Module.

Implementation: DTD

21.1. The caption element

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

21.2. 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.

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.

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

The advantage of using the colgroup attribute is that authors may group information about multiple columns.

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).

21.3. The table element

The table element contains all other elements that specify caption, rows, content, and formatting for a table.

21.3.1. 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. Please consult the section on bidirectional text for more information on text direction issues.

21.3.2. 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.

21.3.2.1. 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
       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.">
<caption>Cups of coffee consumed by each senator</caption>
<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
       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.">
<caption>Cups of coffee consumed by each senator</caption>
<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">
<tbody>
  <tr>
    <th colspan="5" scope="colgroup">Community Courses -- Bath Autumn 1997</th>
  </tr>
  <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>

21.3.2.2. 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
          summary="This table summarizes travel expenses
                   incurred during August trips to
                   San Jose and Seattle">
<caption>Travel Expense Report</caption>
<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 user agents a means to customize rendering (e.g., through style sheets).

21.3.3. Sample table

This sample illustrates grouped rows and columns.

<table
       summary="Calendar for 2002.">
<caption><b>Calendar for 2002</b></caption>
<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
====================================================================

21.4. 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.

21.5. 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 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.">
<caption>Cups of coffee consumed by each senator</caption>
<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

21.5.1. 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>

21.6. 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.

21.7. The tr element

The tr elements acts as a container for a row of table cells. The end tag may be omitted.

<table 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.">
<caption>Cups of coffee consumed by each senator</caption>
<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>

22. XHTML Target Module

This section is normative.

The content of a frame can specify destination targets for a selection. This module adds the target attribute to the area and link defining elements. This is defined as a separate module so it can be included in documents that will be included in frames and documents that use the target feature to open a new window.

Implementation: DTD

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 evaluated in.

XFrames not published yet

We need a reference to XFrames here, but XFrames is not yet public.

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 Schema

This appendix is normative.

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

C. 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.

D. 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.

E. 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.

E.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:

E.1.1. XHTML Base Architecture

E.1.2. XHTML Notations

E.1.3. XHTML Datatypes

E.1.4. XHTML Common Attribute Definitions

E.1.5. XHTML Qualified Names

E.1.6. XHTML Character Entities

E.2. XHTML Module Implementations

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

E.2.1. Structure

E.2.2. Text

E.2.3. Hypertext

E.2.4. Lists

E.2.5. Bi-directional Text

E.2.6. Client-side Image Map

E.2.7. Edit

E.2.8. Link

E.2.9. Metainformation

E.2.10. Object

E.2.11. Presentation

E.2.12. Scripting

E.2.13. Server-side Image Map

E.2.14. Style Sheet

E.2.15. Tables

E.2.16. Target

E.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.

E.3.1. Block Phrasal

E.3.2. Block Presentational

E.3.3. Block Structural

E.3.4. Inline Phrasal

E.3.5. Inline Presentational

E.3.6. Inline Structural

E.3.7. Param

E.3.8. Legacy Redeclarations

F. References

This appendix is normative.

F.1. Normative References

[CSS2]

"Cascading Style Sheets, level 2 (CSS2) Specification", W3C Recommendation, B. Bos, H. W. Lie, C. Lilley, I. Jacobs, eds., 12 May 1998.
Available at: http://www.w3.org/TR/1998/REC-CSS2-19980512

[DOM]

"Document Object Model (DOM) Level 1 Specification", L. Wood et al., 1 October 1998.
Available at: http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001

[HTML4]

"HTML 4.01 Specification: W3C Recommendation", W3C Recommendation, D. Raggett, A. Le Hors, I. Jacobs, eds., 24 December 1999.
Available at: http://www.w3.org/TR/1999/REC-html401-19991224

[ISO639]

"Codes for the representation of names of languages", ISO 639:1988. For more information, consult http://www.iso.ch/cate/d4766.html. Refer also to http://www.oasis-open.org/cover/iso639a.html.

[ISO3166]

"Codes for the representation of names of countries", ISO 3166:1993.

[ISO10646]

"Information Technology -- Universal Multiple-Octet Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane", ISO/IEC 10646-1:2000. This reference refers to a set of codepoints that may evolve as new characters are assigned to them. Also, this reference assumes that the character sets defined by ISO 10646 and [UNICODE] remain character-by-character equivalent. This reference also includes future publications of other parts of 10646 (i.e., other than Part 1) that define characters in planes 1-16.

[MIMETYPES]

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

[PICS]

"Rating Services and Rating Systems (and Their Machinr Readable Descriptions)", W3C Recommendation, J. Miller, et. al., 31 October 1996.
Available at: http://www.w3.org/TR/REC-PICS-services

[RFC822]

"Standard for the format of ARPA Internet Text Messages", RFC 822, David H Crocker, August 13, 1982.
Available at: http://www.ietf.org/rfc/rfc822.txt

[RFC1555]

"Hebrew Character Encoding for Internet Messages", H. Nussbacher and Y. Bourvine, December 1993.
Available at: http://www.ietf.org/rfc/rfc1555.txt

[RFC1556]

""andling of Bi-directional Texts in MIME", H. Nussbacher, December 1993.
Available at: http://www.ietf.org/rfc/rfc1556.txt

[RFC1808]

"Relative Uniform Resource Locators", RFC 1808, R. Fielding, June 1995.
Available at: http://www.ietf.org/rfc/rfc1808.txt

[RFC2045]

"Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, N. Freed, N. Borenstein, November 1996.
Available at: http://www.ietf.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.ietf.org/rfc/rfc2119.txt

[RFC2616]

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

[RFC3066]

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

[RUBY]

Ruby Annotation, W3C Recommendation, Marcin Sawicki, et al., 31 May 2001.
See: 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 http://www.iso.ch/cate/d16387.html for information about the standard, or http://www.oasis-open.org/cover/general.html#overview about SGML.

[SRGB]

"A Standard Default Color Space for the Internet", version 1.10, M. Stokes, M. Anderson, S. Chandrasekar, and R. Motta, 5 November 1996. Available at: http://www.w3.org/Graphics/Color/sRGB

[UNICODE]

"The Unicode Standard", The Unicode Consortium. Version 3.2.0 is defined by: The Unicode Standard, Version 3.0 (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5), as amended by the Unicode Standard Annex #27: Unicode 3.1 (http://www.unicode.org/reports/tr27/) and the Unicode Standard Annex #28: Unicode 3.2 (http://www.unicode.org/reports/tr28/).
For more information about Unicode, see http://www.unicode.org.

[URI]

"Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, T. Berners-Lee, R. Fielding, L. Masinter, August 1998.
Available at: http://www.ietf.org/rfc/rfc2396.txt. This RFC updates RFC 1738 [URL] and [RFC1808].

[URL]

"Uniform Resource Locators (URL)", RFC 1738, T. Berners-Lee, L. Masinter, M. McCahill, December 1994.
Available at: http://www.ietf.org/rfc/rfc1738.txt

[XFORMS]

"XForms 1.0", W3C Working Draft, M. Dubinko et al., 18 January 2002.
Available at: http://www.w3.org/TR/2002/WD-xforms-20020118/

[XHTML1]

"XHTML 1.0: The Extensible HyperText Markup Language (Second Edition)", W3C Recommendation, S. Pemberton et al., 1 August 2002.
Available at: http://www.w3.org/TR/2002/REC-xhtml1-20020801

[XHTMLMOD]

Modularization of XHTML, W3C Recommendation, Murray Altheim, et al., 10 April 2001
See: http://www.w3.org/TR/2001/REC-xhtml-modularization-20010410

[XML]

"Extensible Markup Language (XML) 1.0 (Second Edition)", W3C Recommendation, T. Bray, J. Paoli, C. M. Sperberg-McQueen, E. Maler, eds., 6 October 2000.
Available at: http://www.w3.org/TR/2000/REC-xml-20001006

[XMLNAMES]

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

[XMLEVENTS]

"XML Events", W3C Working Draft, S. McCarron, S. Pemberton, T.V. Raman, eds., 26 October 2001.
Available at: http://www.w3.org/TR/2001/WD-xml-events-20011026

[XMLSCHEMA]

"XML Schema Part 1: Structures", W3C Recommendation, H. S. Thompson, D. Beech, M. Maloney, N. Mendelsohn, 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

F.2. Informative References

[MATHML]

"Mathematical Markup Language (MathML) Version 2.0", W3C Recommendation, D. Carlisle, P. Ion, R. Miner, N. Poppelie, eds., 21 February 2001.
Available at: http://www.w3.org/TR/2001/REC-MathML2-20010221

[SMIL]

"Synchronized Multimedia Integration Language (SMIL) 1.0 Specification", W3C Recommendation, P. Hoschka, ed., 15 June 1998.
Available at: http://www.w3.org/TR/1998/REC-smil-19980615

[XLINK]

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

[XMLSTYLE]

"Associating Style Sheets with XML documents Version 1.0", W3C Recommendation, J. Clark, ed., 29 June 1999.
Available at: http://www.w3.org/1999/06/REC-xml-stylesheet-19990629

G. Acknowledgements

This appendix is informative.

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

This section will be updated at publication time.