XHTML™ Basic

Abstract

The XHTML Basic document type is a subset of XHTML 1.1. It contains the basic XHTML features inlcluding text structure, images, basic forms, and basic tables. It is designed for Web clients that do not support the full set of XHTML features; for example, Web clients such as mobile phones, PDAs, pagers, and settop boxes.

The document type definition is implemented using XHTML modules as defined in "Modularization of XHTML" [XHTMLMOD].

Status of This Document

This document is the first public review draft of the XHTML Basic specification. It has been prepared by the Mobile Subgroup of the W3C HTML Working Group (members only) based on input from the WAP Forum Application's group and members of the W3C Mobile Access Interest Group (members only).

This is work in progress, and does not imply endorsement by, nor the consensus of, either W3C membership, WAP Forum membership, or members of the HTML Working Group or the Mobile Access Interest Group. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than "work in progress". A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR.

This document has been produced as part of the W3C HTML Activity. This document will be used by the Mobile Subgroup of the W3C HTML Working Group and the W3C Mobile Access Interest Group to find a common ground for future markup languages aimed at content for small information appliances.

We explicitly invite comments on this specification. Please send them to www-html-editor@w3.org. Public discussion of HTML takes place on www-html@w3.org (archived). To subscribe send an email to <www-html-request@w3.org> with the word subscribe in the subject line.

Table of Contents

1. Introduction

1.1 XHTML for Small Information Appliances

HTML 4.0 was designed for large devices, overlapping windows/frames menus, mouse input pointing device, high powered CPU, unlimited power supply. Requiring a full fledge computer for access to the World Wide Web excludes a large portion of the population from consumer device access of online information and services.

Because there are many ways to subset HTML, there are many almost identical subsets defined by organizations and companies. Without a common base set of features, developing applications for a wide range of Web clients is difficult. Transformation between XHTML based languages is easier if they share a common set of elements. The goal of XHTML Basic is to converge various HTML subset into one common subset of XHTML.

The document type definition for XHTML Basic is implemented based on the XHTML modules defined in Modularized XHTML [XHTMLMOD].

1.2 Background and Requirements

Information appliances are targeted for particular uses. They support the features they need for the functions they are designed to fulfill. The following are examples of different information appliances:

• Mobile phones
• Televisions
• PDAs
• Vending machines
• Pagers
• Car navigation systems
• Mobile game machines
• Digital book readers
• Smart watches

Existing subsets and variants of HTML for these clients include "Compact HTML" [CHTML], the Wireless Markup Language [WML], and the "HTML 4.0 Guidelines for Mobile Access" [GUIDELINES]. The common features found in these document types include:

• Basic text (including headings, paragraphs, and lists)
• Hyperlinks and links to related documents
• Basic forms
• Basic tables
• Images
• Meta information

This set of HTML features has been the starting point for the design of XHTML Basic. The fact that most content developers are familiar with HTML makes it appropriate as a host language, that include markup modules from other languages using the methods described in "Building XHTML Modules" [XHTMLMOD]. For example, XHTML Basic may be extended with an Event Module that is more generic than the traditional HTML 4.0 event system.

The intention with the simple design of XHTML Basic is not to limit the functionality of future languages for small appliances to only what is defined in this specification. But since the features in HTML 4.0 (frames, advanced tables, fixed set of attribute event handlers, and objects) were developed for a desktop computer type of client, they have proved to be inappropriate for many non-desktop devices. We believe XHTML Basic will be extended and built upon. Extending XHTML from a common and basic set of features, instead of many almost identical subsets or the too large set of functions in HTML 4.0, we think is good for the interoperability on the Web, as well as scalability. Compared to the rich functionality of HTML 4.0, XHTML Basic may look like one step back, but in fact, it is two steps forward for clients that do not need what is in HTML 4.0 and for content developers that get one XHTML subset instead of many.

1.3 Design Rationale

This section explains why certain HTML features are not part of XHTML Basic.

1.3.1 Style Sheets

The style attribute and the style element are not supported. External Style sheets are recommended. The link element can be used to include an external style sheets. The div and span elements and the class attribute are supported to hook style information onto the structure. Separation between structure and presentation allows user agents to download the style sheets if they support style sheets; user agents that do not support style sheets can ignore the external stylesheet. The media attribute can be used to select the appropriate stylesheets. See section 14.2.4 in the HTML 4.0 specification [HTML40] for more details.

1.3.2 Script and Events

The script and noscript elements are not supported. Usually small devices have limited memory and CPU power. Execution of script programs may not be supported. Contents should be readable even if scripts are not executed.

Also, just as in the case for style sheets, scripts can be included by reference.

Event handler attributes used to invoke script programs are not supported. Events are device dependent. An incoming-call event is unlikely to happen in a television. A generic event handling mehanism would be more appropriate than hardwiring the event names in the document type definition.

1.3.3 Presentation

Many simple Web clients cannot display text that is more complex than mono-space. Bi-directional text, bold faced font, and other text extension elements are not supported.

It is recommended that style sheets are used to create a presentation that is appropriate for the device.

1.3.4 Forms

Basic XHTML forms are supported. But only devices with a local file system can take advantage of file and image input types in forms, so they are not included in the basic feature set. The optgroup and fieldset are redundant means of expressing selection from a list and are not needed in the basic set. Also, content developers should keep in mind that users may not be able to input many characters from some devices (e.g a mobile phone).

1.3.5 Tables

Basic XHTML tables are supported, but for the same reason as for forms, the number or elements has been limited. The thead, tfoot, tbody, col and colgroup are not supported.

Tables can be difficult to display on small devices. Content developers are recommended to follow the accessability guidelines for tables [WAI-WEBCONTENT].

1.3.6 Frames

Frames are not supported. Frames depend on screen interface and are not part of XHTML 1.1.

1.3.7 Objects

Simple Web clients may support images as embedded objects. The object and param elements are not supported. Limited input capabilities, for example no pointing device, has excluded image-maps.

2 Conformance

This section is normative.

2.1 Document Conformance

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

1. It must validate against the DTD found in Appendix B.
2. The root element of the document must be <html>.
3. The name of the default namespace on the root element must be the XHTML namespace name, http://www.w3.org/1999/xhtml.
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 B using its Formal Public Identifier. The system identifier may be modified appropriately.

   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
   	"xhtml10-basic.dtd">
   

2.2 User Agent Conformance

The user agent must conform to the "User Agent Conformance" section of the XHTML specification [XHTML1].

3. Document Type Definition

This section is normative.

The XHTML Basic document type is defined as a set of XHTML modules. All XHTML modules are defined in the "Modularization of XHTML" specification [XHTMLMOD].

XHTML Basic consists of the following XHTML 1.1 modules:

Structure Module

body, div, head, html, span, title

Basic Text Module

abbr, acronym, address, blockquote, br, cite, code, dfn, em, h1, h2, h3, h4, h5, h6, kbd, p, pre, q, samp, strong, var

Hypertext Module

a

List Module

dl, dt, dd, ol, ul, li

Basic Forms Module

form, input, select, option, textarea

Basic Tables Module

caption, table, td, th, tr

Image Module

img

Meta Information Module

meta

Link Module

link

Base Module

base

An XML 1.0 DTD is available in Appendix B.

4 How to Use XHTML Basic

Although XHTML Basic can be used as it is, - a simple XHTML language with text, links, and images -, the intention with its simple design is to use it as a host language. A host language can contain a mix of vocabularies all rolled into one document type. It is natural that XHTML is the host language, since that is what most Web developers are used to.

When markup from other languages is added to XHTML Basic, the resulting document type will be an extension of XHTML Basic. Content developers can develop for the XHTML Basic or take advantage of the extensions. The point is that XHTML Basic always is the common language that user agents supports. See "Building XHTML Modules" [BUILDING] for information about how to define markup language modules that are compatible with the modularization framework used by XHTML.

5 Acknowledgements

Thanks to Gary Adams (Sun), Johan Hjelm (W3C/Ericsson), Wayne Carr (Intel) and the W3C HTML Working Group for contributing, reviewing and commenting on this document.

A. References

A.1. Normative References

[BUILDING]

"Building XHTML Modules", W3C Working Draft, M. Altheim, S. McCarron, eds., 10 September 1999. Available at: http://www.w3.org/TR/1999/WD-xhtml-building-19990910.
The latest version is available at: http://www.w3.org/TR/xhtml-building

[HTML40]

"HTML 4.0 Specification", W3C Recommendation, D. Raggett, A. Le Hors, I. Jacobs, eds., 18 December 1997, revised 24 April 1998. Available at: http://www.w3.org/TR/1998/REC-html40-19980424.
The latest version is available at: http://www.w3.org/TR/REC-html40

[XHTML1]

"XHTML 1.0: The Extensible HyperText Markup Language - A Reformulation of HTML 4.0 in XML 1.0", W3C Working Draft, Steven Pemberton et al., 24 November 1999. Available at: http://www.w3.org/TR/1999/WD-xhtml1-19991124
The latest version is available at: http://www.w3.org/TR/xhtml1

[XHTML11]

"XHTML 1.1 - Module-based XHTML", W3C Working Draft, M. Altheim, S. McCarron, eds., 10 September 1999. Available at: http://www.w3.org/TR/1999/WD-xhtml11-19990910
The latest version is available at: http://www.w3.org/TR/xhtml11

[XHTMLMOD]

"Modularization of XHTML", W3C Working Draft, M. Altheim et al., eds., 10 September 1999. Available at: http://www.w3.org/TR/1999/WD-xhtml-modularization-19990910
The latest version is available at: http://www.w3.org/TR/xhtml-modularization

[XML]

"Extensible Markup Language (XML) 1.0", W3C Recommendation, T. Bray, J. Paoli, C. M. Sperberg-McQueen, eds., 10 February 1998. Available at: http://www.w3.org/TR/1998/REC-xml-19980210
The latest version is available at: http://www.w3.org/TR/REC-xml

A.2. Informative References

[CHTML]

"Compact HTML for Small Information Appliances", W3C Note, T. Kamada, 9 February 1998. Available at: http://www.w3.org/TR/1998/NOTE-compactHTML-19980209

[GUIDELINES]

"HTML 4.0 Guidelines for Mobile Access, W3C Note, T. Kamada, T. Asada, M. Ishikawa, S. Matsui, eds., 15 March 1999. Available at: http://www.w3.org/TR/1999/NOTE-html40-mobile-19990315
The latest version is available at: http://www.w3.org/TR/NOTE-html40-mobile

[WAI-WEBCONTENT]

"Web Content Accessibility Guidelines 1.0", W3C Recommendation, W. Chisholm, G. Vanderheiden, I. Jacobs, eds., 5 May 1999. Available at: http://www.w3.org/TR/1999/WAI-WEBCONTENT019990505
The latest version is available at: http://www.w3.org/TR/WAI-WEBCONTENT

[WML]

"Wireless Markup Language Specification", WAP Forum Ltd. Available from http://www.wapforum.org/what/technical.htm

B. Document Type Definition

<!-- XHTML Basic 1.0 DTD  .................................................. -->
<!-- file: xhtml10-basic.dtd -->

<!-- XHTML Basic 1.0 DTD

     This is XHTML Basic 1.0, a proper subset of XHTML 1.1.

     Copyright 1998-1999 World Wide Web Consortium
        (Massachusetts Institute of Technology, Institut National de
         Recherche en Informatique et en Automatique, Keio University).
         All Rights Reserved.

     Permission to use, copy, modify and distribute the XHTML 1.1 DTD and
     its accompanying documentation for any purpose and without fee is
     hereby granted in perpetuity, provided that the above copyright notice
     and this paragraph appear in all copies.  The copyright holders make
     no representation about the suitability of the DTD for any purpose.

     It is provided "as is" without expressed or implied warranty.

        Editors:    Murray M. Altheim <mailto:altheim@eng.sun.com>
                    Peter Stark       <mailto:stark@corp.phone.com>
        Revision:   $Id: xhtml10-basic.dtd,v 1.4 1999/11/25 09:55:31 altheim Exp $ SMI

-->
<!-- This is the driver file for version 1.0 of the XHTML Basic DTD.

     Please use this formal public identifier to identify it:

         "-//W3C//DTD XHTML Basic 1.0//EN"
-->
<!ENTITY % XHTML.version  "-//W3C//DTD XHTML Basic 1.0//EN" >

<!-- Use this URI to identify the default namespace:

         "http://www.w3.org/1999/xhtml"
-->
<!ENTITY % XHTML.ns  "http://www.w3.org/1999/xhtml" >

<!-- Reserved for use with the XLink namespace:
-->
<!ENTITY % XLINK.ns "" >

<!-- For example, if you are using XHTML Basic 1.0 directly, use
     the FPI in the DOCTYPE declaration, with the xmlns attribute
     on the document element to identify the default namespace:

         <?xml version="1.0"?>
         <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                               "xhtml10-basic.dtd" >
         <html xmlns="http://www.w3.org/1999/xhtml"
               xmlns:xlink="http://www.w3.org/XML/XLink/0.9"
               xml:lang="en" >
         ...
         </html>
-->

<!-- reserved for future use with document profiles -->
<!ENTITY % XHTML.profile  "" >

<!-- Internationalization features
     This feature-test entity is used to declare elements
     and attributes used for internationalization support.
-->
<!ENTITY % XHTML.I18n            "INCLUDE" >

<!-- :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -->

<!ENTITY % xhtml-events.module   "IGNORE" >
<!ENTITY % xhtml-datatypes.mod
     PUBLIC "-//W3C//ENTITIES XHTML Basic 1.0 Datatypes 1.0//EN"
            "xhtml10-basic-datatypes-1.mod" >
<!ENTITY % xhtml-model.mod
     PUBLIC "-//W3C//ENTITIES XHTML Basic 1.0 Document Model 1.0//EN"
            "xhtml10-basic-model-1.mod" >
<!ENTITY % xhtml-inlpres.module  "IGNORE" >
<!ENTITY % xhtml-edit.module     "IGNORE" >
<!ENTITY % xhtml-bdo.module      "IGNORE" >
<!ENTITY % xhtml-csismap.mod     "IGNORE" >

<!-- :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -->

<!ENTITY % xhtml-framework.mod
     PUBLIC "-//W3C//ENTITIES XHTML 1.1 Modular Framework 1.0//EN"
            "xhtml11-framework-1.mod" >
%xhtml-framework.mod;

<!ENTITY % Pre.content
     "( #PCDATA
      | %Inlstruct.class;
      %Inlphras.class;
      %Anchor.class;
      %Inline.extra; )*"
>

<!ENTITY % xhtml-text.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Basic Text 1.0//EN"
            "xhtml11-text-1.mod" >
%xhtml-text.mod;

<!ENTITY % xhtml-image.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Images 1.0//EN"
            "xhtml11-image-1.mod" >
%xhtml-image.mod;

<!ENTITY % xhtml-hypertext.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Hypertext 1.0//EN"
            "xhtml11-hypertext-1.mod" >
%xhtml-hypertext.mod;

<!ENTITY % xhtml-list.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Lists 1.0//EN"
            "xhtml11-list-1.mod" >
%xhtml-list.mod;

<!ENTITY % xhtml-form.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Basic Forms 1.0//EN"
            "xhtml11-formb-1.mod" >
%xhtml-form.mod;

<!ENTITY % xhtml-table.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Basic Tables 1.0//EN"
            "xhtml11-tableb-1.mod" >
%xhtml-table.mod;

<!ENTITY % xhtml-meta.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Metainformation 1.0//EN"
            "xhtml11-meta-1.mod" >
%xhtml-meta.mod;

<!ENTITY % xhtml-link.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Link Element 1.0//EN"
            "xhtml11-link-1.mod" >
%xhtml-link.mod;

<!ENTITY % xhtml-base.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Base Element 1.0//EN"
            "xhtml11-base-1.mod" >
%xhtml-base.mod;

<!ENTITY % xhtml-struct.mod
     PUBLIC "-//W3C//ELEMENTS XHTML 1.1 Document Structure 1.0//EN"
            "xhtml11-struct-1.mod" >
%xhtml-struct.mod;

<!-- end of XHTML Basic 1.0 DTD  ........................................... -->