Modularization of XHTML - XHTML Abstract Modules

This section specifies the contents of the XHTML abstract modules. These modules are abstract definitions of collections of elements, attributes, and their content models. These abstract modules can be mapped onto any appropriate specification mechanism. The XHTML 1.1 Specification, for example, maps these modules onto DTDs as described in [XML].

Content developers and device designers should view this section as a guide to the definition of the functionality provided by the various XHTML-defined modules. When developing documents or defining a profile for a class of documents, content developers can determine which of these modules are essential for conveying their message. When designing clients, device designers should develop their device profiles by choosing from among the abstract modules defined here.

4.1. Common Characteristics of Modules

Many of the abstract modules in this section describe elements, attributes on those elements, and minimal content models for those elements or element sets. This section identifies some shorthand expressions that are used throughout the abstract module definitions. 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.

4.1.1. Syntactic Conventions

The abstract modules are not defined in a formal grammar. However, the definitions do adhere to the following syntactic conventions (as defined in Building XHTML Modules [BUILDING]). 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 or 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 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 verical bars |, inside of parentheses following the attribute name.

4.1.2. Content Types

The abstract module definitions in this document 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.

4.1.3. Attribute Types

In some instances, the types of attribute values or the explicit set of permitted values for attributes are defined. The following attribute types (defined in the XML 1.0 Recommendation) are used in the definitions of the Abstract Modules:

Attribute Type	Definition
CDATA	Character data
ID	A document-unique identifier
IDREF	A reference to a document-unique identifier
NAME	A name with the same character constraints as ID above
NMTOKEN	A name composed of CDATA characters but no whitespace
NMTOKENS	Multiple names composed of CDATA characters separated by whitespace
PCDATA	Processed character data

4.1.4. Attribute Collections

The following basic attribute sets are used on many elements. In each case where they are used, their use is identified via their name rather than enumerating the list.

Collection Name	Attributes in Collection
Core	class (NMTOKEN), id (ID), title (CDATA)
I18N	dir ("rtl" \| "ltr"), xml:lang (NMTOKEN)
Events	onclick, ondblclick, onmousedown, onmouseup, onmouseover, onmousemove, onmouseout, onkeypress, onkeydown, onkeyup
Style	style (CDATA)
Common	Core + Events + Internationalization + Style

Note that the Events collection is only defined when the Intrinsic Events abstract module is selected. Otherwise, the Events collection is empty.

Also note that the Style collection is only defined when the Stylesheet Module is selected. Otherwise, the Style collection is empty.

4.2. Basic Modules

4.2.1. Structure Module

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:

Elements	Attributes	Minimal Content Model
body	Common	(Heading \| Block \| List)*
div	Common	(Heading \| Block \| List)*
head	I18n, profile	title
html	I18n, version, xmlns	head, body
span	Common	(PCDATA \| Inline)*
title	I18n	PCDATA

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

div

element is added to the Block content set and the span element is added to the Inline content set as these are defined in the Basic Text Module below.

4.2.2. Basic Text Module

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

Element	Attributes	Minimal Content Model
abbr	Common	(PCDATA \| Inline)*
acronym	Common	(PCDATA \| Inline)*
address	Common	(PCDATA \| Inline)*
blockquote	Common, cite	(PCDATA \| Heading \| Block)*
br	Core	EMPTY
cite	Common	(PCDATA \| Inline)*
code	Common	(PCDATA \| Inline)*
dfn	Common	(PCDATA \| Inline)*
em	Common	(PCDATA \| Inline)*
h1	Common	(PCDATA \| Inline)*
h2	Common	(PCDATA \| Inline)*
h3	Common	(PCDATA \| Inline)*
h4	Common	(PCDATA \| Inline)*
h5	Common	(PCDATA \| Inline)*
h6	Common	(PCDATA \| Inline)*
kbd	Common	(PCDATA \| Inline)*
p	Common	(PCDATA \| Inline)*
pre	Common	(PCDATA \| Inline)*
q	Common	(PCDATA \| Inline)*
samp	Common	(PCDATA \| Inline)*
strong	Common	(PCDATA \| Inline)*
var	Common	(PCDATA \| Inline)*

4.2.3. Hypertext Module

The Hypertext Module provides the element that is used to define hypertext links to other resources. This module supports the following element and attributes:

Element	Attributes	Minimal Content Model
a	Common, charset, href, hreflang, rel, rev, type	(PCDATA \| Inline - a)*

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

4.2.4. List Module

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

Elements	Attributes	Minimal Content Model
dl	Common	(dt \| dd)+
dt	Common	(PCDATA \| Inline)*
dd	Common	(PCDATA \| Inline)*
ol	Common	li+
ul	Common	li+
li	Common	(PCDATA \| Inline)*

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

4.3. Applet Module

The Applet Module provides elements for referencing external applications. Specifically, the Applet Module supports the following elements and attributes:

Element	Attributes	Minimal Content Model
applet	Core, alt, archive, code, codebase, height, name, object, width	param?
param	id (ID), name (CDATA), type, value, valuetype	EMPTY

When the Applet Module is used, it adds the


      applet

element to the Inline content set of the Basic Text Module.

4.4. Text Extension Modules

4.4.1. Presentation Module

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

Element	Attributes	Minimal Content Model
b	Common	(PCDATA \| Inline)*
big	Common	(PCDATA \| Inline)*
hr	Common	EMPTY
i	Common	(PCDATA \| Inline)*
small	Common	(PCDATA \| Inline)*
sub	Common	(PCDATA \| Inline)*
sup	Common	(PCDATA \| Inline)*
tt	Common	(PCDATA \| Inline)*

When this module is used, the hr element is added to the Block content set of the Basic Text Module. In additional, the

b, big, i,
      small, sub, sup,

and tt elements are added to the Inline content set of the Basic Text Module.

4.4.2. Edit Module

Element	Attributes	Minimal Content Model
del	Common	(PCDATA \| Inline)*
ins	Common	(PCDATA \| Inline)*

When this module is used, the del and

ins

elements are added to the Inline content set of the Basic Text Module.

4.4.3. BDO Module

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

Elements	Attributes	Minimal Content Model
bdo	Common	(PCDATA \| Inline)*

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

4.5. Forms Modules

4.5.1. Basic Forms Module

The Basic Forms Module provides the forms features found in HTML 3.2. Specifically, the Basic Forms Module supports the following elements, attributes, and minimal content model:

When this module is used, it adds the Form content set to the Block content set and it adds the Formctrl content set to the Inline content set as these are defined in the Basic Text Module.

Elements	Attributes	Minimal Content Model
form	Common, action, method, enctype	Heading \| Block - form
input	Common, checked, maxlength, name, size, src, type, value	EMPTY
select	Common, multiple, name, size	option+
option	Common, selected, value	Inline*
textarea	Common, columns, name, rows	PCDATA*

4.5.2. Forms Module

The Forms Module provides all of the forms features found in HTML 4.0. Specifically, the Forms Module supports:

When this module is used, it adds the Form content set to the Block content set and it adds the Formctrl content set to the Inline content set as these are defined in the Basic Text Module.

The Forms Module is a superset of the Basic Forms Module. These modules may not be used together in a single document type.

Elements	Attributes	Minimal Content Model
form	Common, accept, accept-charset, action, method, enctype	(Heading \| Block - form \| fieldset)+
input	Common, accept, accesskey, alt, checked, disabled, maxlength, name, readonly, size, src, tabindex, type, value	EMPTY
select	Common, disabled, multiple, name, size, tabindex	(optgroup \| option)+
option	Common, disabled, label, selected, value	PCDATA
textarea	Common, accesskey, columns, disabled, name, readonly, rows, tabindex	PCDATA
button	Common, accesskey, disabled, name, tabindex, type, value	(PCDATA \| Heading \| List \| Block - Form \| Inline - Formctrl)*
fieldset	Common	(PCDATA \| legend \| Flow)*
label	Common, accesskey, for	(PCDATA \| Inline - label)*
legend	Common, accesskey	(PCDATA \| Inline)+
optgroup	Common, disabled, label	option+

4.6. Table Modules

4.6.1. Basic Tables Module

The Basic Tables Module provides table-related elements, but only in a limited form. Specifically, the Basic Tables Module supports:

Elements	Attributes	Minimal Content Model
caption	Common	(PCDATA \| Inline)*
table	Common, border, cellpadding. cellspacing, summary, width	caption?, tr+
td	Common, abbr, align, axis, colspan, headers, rowspan, scope, valign	(PCDATA \| Flow)*
th	Common, abbr, align, axis, colspan, headers, rowspan, scope, valign	(PCDATA \| Flow)*
tr	Common, align, valign	(th \| td)+

When this module is used, it adds the table element to the Block content set as defined in the Basic Text Module.

4.6.2. Tables Module

As its name suggests, the Tables Module provides table-related elements that are better able to be accessed by non-visual user agents. Specifically, the Tables Module supports the following elements, attributes, and content model:

Elements	Attributes	Minimal Content Model
caption	Common	(PCDATA \| Inline)*
table	Common, border, cellpadding. cellspacing, datapagesize, frame, rules, summary, width	caption?, ( col* \| colgroup* ), (( thead?, tfoot?, tbody+ ) \| ( tr+ ))
td	Common, abbr, align, axis, colspan, headers, rowspan, scope, valign	(PCDATA \| Inline)*
th	Common, abbr, align, axis, colspan, headers, rowspan, scope, valign	(PCDATA \| Inline)*
tr	Common, align, valign	(td \| th)+
col	Common, align, span, valign, width	EMPTY
colgroup	Common, align, span, valign, width	col*
tbody	Common, align, valign	tr+
thead	Common, align, valign	tr+
tfoot	Common, align, valign	tr+

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

4.7. Image Module

The Image Module provides basic image embedding, and may be used in some implementations independently of client side image maps. The Image Module supports the following element and attributes:

Elements	Attributes	Minimal Content Model
img	Common, alt, height, longdesc, src, width	EMPTY

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

4.8. Client-side Image Map Module

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:

Elements	Attributes	Minimal Content Model
a&	coords, shape	n/a
area	Common, accesskey, alt, coords, href, nohref, shape, tabindex	EMPTY
img&	usemap	n/a
map	Common, name	((Heading \| Block) \| area)+
object&	usemap	Note: Only when the object module is included

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

4.9. Server-side Image Map Module

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

Elements	Attributes	Minimal Content Model
img&	ismap	n/a

4.10. Object Module

The Object Module provides elements for general-purpose object inclusion. Specifically, the Object Module supports:

Elements	Attributes	Minimal Content Model
object	Common, archive, classid, codebase, codetype, data, declare, height, standby, tabindex, type, width	(PCDATA \| Flow \| param)*
param	id, type, value, valuetype	EMPTY

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

4.11. Frames Module

As its name suggests, the Frames Module provides frame-related elements. Specifically, the Frames Module supports:

Elements	Attributes	Minimal Content Model
frameset	Core, cols, rows	(frame \| noframes)+
frame	Core, frameborder, longdesc, marginheight, marginwidth, noresize, scrolling, src	EMPTY
noframes	Common	body
a&	target	n/a

4.12. Iframe Module

The Iframe Module defines an element that can be used to define a base URL against which relative URIs in the document will be resolved. The element and attribute included in this module are:

Elements	Attributes	Minimal Content Model
iframe	Core, frameborder, height, longdesc, marginheight, marginwidth, scrolling, src, width	Flow

When this module is used, the iframe element is added to the Block content set as defined by the Basic Text Module.

4.13. Intrinsic Events

Intrinsic events are attributes that are used in conjunction with elements that can have specific actions occur when certain events are performed by the user. The attributes indicated in the following table are added to the attribute set for their respective elements ONLY when the modules defining those elements are selected. Note also that selection of this module defines the attribute collection Events as described above. Attributes defined by this module are:

Elements	Attributes	Notes
a&	onblur, onfocus
area&	onblur, onfocus	When the Client-side Image Map module is also used
form&	onreset, onsubmit	When the Basic Forms or Forms module is used
body&	onload, onunload
label&	onblur, onfocus	When the Forms module is used
input&	onblur, onchange, onfocus, onselect	When the Basic Forms or Forms module is used
select&	onblur, onchange, onfocus	When the Basic Forms or Forms module is used
textarea&	onblur, onchange, onfocus, onselect	When the Basic Forms or Forms module is used
button&	onblur, onfocus	When the Forms module is used

4.14. Metainformation Module

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:

Elements	Attributes	Minimal Content Model
meta	I18n, content, http-equiv, name, scheme	EMPTY

4.15. Scripting Module

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:

Elements	Attributes	Minimal Content Model
noscript	Common	(Heading \| List \| Block)+
script	charset, defer, src, type	PCDATA

When this module is used, it adds the

script and
      noscript

elements are added to the Block content set of the Basic Text Module.

4.16. Stylesheet Module

The Stylesheet Module enables style sheet processing. Note also that selection of this module defines the attribute collection Style as described above. The element and attributes defined by this module are:

Elements	Attributes	Minimal Content Model
style	I18n, media, title, type	PCDATA

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

4.17. Link Module

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:

Elements	Attributes	Minimal Content Model
link	Common, charset, href, hreflang, media, rel, rev, type	EMPTY

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

4.18. Base Module

The Base Module defines an element that can be used to define a base URL against which relative URIs in the document will be resolved. The element and attribute included in this module are:

Elements	Attributes	Minimal Content Model
base	href	EMPTY

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

4. XHTML Abstract Modules