W3C XHTML(TM) Basic W3C Recommendation 19 December 2000 This version: http://www.w3.org/TR/2000/REC-xhtml-basic-20001219 (Plain text version, PostScript version, PDF version, ZIP archive, or Gzip'd TAR archive) Latest version: http://www.w3.org/TR/xhtml-basic Previous version: http://www.w3.org/TR/2000/PR-xhtml-basic-20001103 Editors: Mark Baker, Sun Microsystems Masayasu Ishikawa, W3C Shinichi Matsui, Panasonic Peter Stark, Ericsson Ted Wugofski, Openwave Systems Toshihiko Yamakami, ACCESS Co., Ltd. Copyright © 1999-2000 W3C® (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply. _________________________________________________________________ Abstract The XHTML Basic document type includes the minimal set of modules required to be an XHTML host language document type, and in addition it includes images, forms, basic tables, and object support. 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 is rich enough for content authoring. XHTML Basic is designed as a common base that may be extended. For example, an event module that is more generic than the traditional HTML 4 event system could be added or it could be extended by additional modules from XHTML Modularization such as the Scripting Module. The goal of XHTML Basic is to serve as a common language supported by various kinds of user agents. The document type definition is implemented using XHTML modules as defined in "Modularization of XHTML" [XHTMLMOD]. 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 has been reviewed by W3C Members and other interested parties and has been endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited as a normative reference from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web. This document has been produced by the W3C HTML Working Group (members only) as part of the W3C HTML Activity. It integrates feedback from the WAP Forum and members of the W3C Mobile Access Interest Group (members only). This document will be used by 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. "Modularization of XHTML" [XHTMLMOD] defines the XHTML modules used in the XHTML Basic document type. At the time of this publication, the Candidate Recommendation review period for "Modularization of XHTML" has closed. Based on that review, the W3C HTML Working Group believes that the definition of modules used in XHTML Basic is stable, and the Working Group does not expect to make changes to "Modularization of XHTML" that would be incompatible with XHTML Basic. Public discussion of HTML 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). The list of known errors in this document is available at http://www.w3.org/2000/12/REC-xhtml-basic-20001219-errata. The English version of this specification is the only normative version. Information about translations of this document is available at http://www.w3.org/MarkUp/translations. A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR. Table of Contents 1. Introduction 1.1. XHTML for Small Information Appliances 1.2. Background and Requirements 1.3. Design Rationale 2. Conformance 2.1. Document Conformance 2.2. User Agent Conformance 3. The XHTML Basic Document Type 4. How to Use XHTML Basic 5. Acknowledgements A. References A.1. Normative References A.2. Informative References B. XHTML Basic Document Type Definition B.1. SGML Open Catalog Entry for XHTML Basic B.2. XHTML Basic Driver B.3. XHTML Basic Customizations 1. Introduction 1.1. XHTML for Small Information Appliances HTML 4 is a powerful language for authoring Web content, but its design does not take into consideration issues pertinent to small devices, including the implementation cost (in power, memory, etc.) of the full feature set. Consumer devices with limited resources cannot generally afford to implement the full feature set of HTML 4. Requiring a full-fledged 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. The motivation for XHTML Basic is to provide an XHTML document type that can be shared across communities (e.g. desktop, TV, and mobile phones), and that is rich enough to be used for simple content authoring. New community-wide document types can be defined by extending XHTML Basic in such a way that XHTML Basic documents are in the set of valid documents of the new document type. Thus an XHTML Basic document can be presented on the maximum number of Web clients. The document type definition for XHTML Basic is implemented based on the XHTML modules defined in Modularization of 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. Since many content developers are familiar with these HTML features, they comprise a useful host language that may be combined with markup modules from other languages according to the methods described in "Modularization of XHTML" [XHTMLMOD]. For example, XHTML Basic may be extended with an event module that is more generic than the traditional HTML 4 event system or it could be extended by additional modules from XHTML Modularization such as the Scripting Module. It is not the intention of XHTML Basic to limit the functionality of future languages. But since the features in HTML 4 (frames, advanced tables, a fixed set of attribute event handlers, etc.) were developed for a desktop computer type of client, they have proved to be inappropriate for many non-desktop devices. XHTML Basic will be extended and built upon. Extending XHTML from a common and basic set of features, instead of almost identical subsets or the too-large set of functions in HTML 4, will be good for interoperability on the Web, as well as for scalability. Compared to the rich functionality of HTML 4, 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 and for content developers who 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 element is not supported. External style sheets are recommended. The link element can be used to include 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 style sheets. See the section on "Media types" in the HTML 4.01 specification ([HTML4], section 14.2.4) 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. 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 mechanism would be more appropriate than hardwiring the event names in the document type definition. 1.3.3. Presentation Many simple Web clients cannot display fonts other than monospace. Bi-directional text, bold faced font, and other text extension elements are not supported. It is recommended that style sheets be used to create a presentation that is appropriate for the device. 1.3.4. Forms Basic XHTML forms ([XHTMLMOD], section 5.5.1) are supported. Since only devices with a local file system can take advantage of file and image input types in forms, they are not included in the basic forms. Also, content developers should keep in mind that users may not be able to input many characters from some devices (e.g. from a mobile phone). 1.3.5. Tables Basic XHTML tables ([XHTMLMOD], section 5.6.1) are supported, but tables can be difficult to display on small devices. It is recommended that content developers follow the Web Content Accessibility Guidelines 1.0 for creating accessible tables ([WCAG10], Guideline 5). Note that in the Basic Tables Module, nesting of tables is prohibited. 1.3.6. Frames Frames are not supported. Frames depend on a screen interface and may not be applicable to some small appliances like phones, pagers, and watches. 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. The document must conform to the constraints expressed in Appendix B. 2. The root element of the document must be . 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. 5. The DTD subset must not be used to override any parameter entities in the DTD. 2.2. User Agent Conformance The user agent must conform to the "User Agent Conformance" section of the XHTML 1.0 specification ([XHTML1], section 3.2). 3. The XHTML Basic Document Type 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 modules: Structure Module* body, head, html, title Text Module* abbr, acronym, address, blockquote, br, cite, code, dfn, div, em, h1, h2, h3, h4, h5, h6, kbd, p, pre, q, samp, span, strong, var Hypertext Module* a List Module* dl, dt, dd, ol, ul, li Basic Forms Module form, input, label, select, option, textarea Basic Tables Module caption, table, td, th, tr Image Module img Object Module object, param Metainformation Module meta Link Module link Base Module base (*) = This module is a required XHTML Host Language module. An XML 1.0 DTD is available in Appendix B. NOTE: Since the HTML event handler attributes are not included in XHTML Basic, form controls outside forms may not function as expected by the user. 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 of its simple design is for use 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 XHTML Basic or take advantage of the extensions. The goal of XHTML Basic is to serve as a common language supported by various kinds of user agents. 5. Acknowledgements This specification was prepared by the W3C HTML Working Group. The members were: * Steven Pemberton, CWI (HTML Working Group Chair) * Robert Adams, Intel (until November 2000) * Murray Altheim, Sun Microsystems * Takuya Asada, W3C (until October 2000) * Daniel Austin, Mozquito Technologies * Mark Baker, Sun Microsystems * Wayne Carr, Intel * Tantek Çelik, Microsoft * Andrew W. Donoho, IBM * Herman Elenbaas, Philips Electronics * Beth Epperson, Netscape/AOL * Masayasu Ishikawa, W3C (HTML Activity Lead) * Shin'ichi Matsui, Panasonic * Shane McCarron, Applied Testing and Technology * Ann Navarro, WebGeek, Inc. * Dave Raggett, W3C/Openwave Systems * Sebastian Schnitzenbaumer, Mozquito Technologies (until September 2000) * Peter Stark, Ericsson * Michel Suignard, Microsoft * Markku Vartiainen, Openwave Systems * Jeremy Wadsworth, Quark Inc. * Malte Wedel, Mozquito Technologies * Linda Welsh, Intel * Ted Wugofski, Openwave Systems Thanks to Gary Adams (Sun Microsystems), Jonny Axelsson (Metastasis design), Peter Chen (Philips), Dan Connolly (W3C), John Cowan (Reuters), Martin J. Dürst (W3C), Johan Hjelm (Ericsson), Ian Jacobs (W3C), Susan Lesch (W3C), Louis Theran (Nokia), Quinton Zondervan (Lotus), members of the W3C Mobile Access Interest Group, the W3C Synchronized Multimedia Working Group, the W3C WAI Protocols and Formats Working Group, and the WAP Forum, for contributing, reviewing and commenting on this document. A. References A.1. Normative References [HTML4] "HTML 4.01 Specification", W3C Recommendation, D. Raggett, A. Le Hors, I. Jacobs, eds., 24 December 1999. Available at: http://www.w3.org/TR/1999/REC-html401-19991224 The latest version is available at: http://www.w3.org/TR/html4 [XHTML1] "XHTML 1.0: The Extensible HyperText Markup Language - A Reformulation of HTML 4 in XML 1.0", W3C Recommendation, Steven Pemberton et al., 26 January 2000. Available at: http://www.w3.org/TR/2000/REC-xhtml1-20000126 The latest version is available at: http://www.w3.org/TR/xhtml1 [XHTMLMOD] "Modularization of XHTML", W3C Candidate Recommendation, R. Adams, M. Altheim, F. Boumphrey, S. Dooley, S. McCarron, S. Schnitzenbaumer, T. Wugofski, eds., 20 October 2000. Available at: http://www.w3.org/TR/2000/CR-xhtml-modularization-20001020 The latest version is available at: http://www.w3.org/TR/xhtml-modularization [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 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 [WCAG10] "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-WEBCONTENT-19990505 The latest version is available at: http://www.w3.org/TR/WCAG10 [WML] "Wireless Markup Language Specification", WAP Forum Ltd. Available from http://www.wapforum.org/what/technical.htm B. XHTML Basic Document Type Definition This appendix is normative. B.1. SGML Open Catalog Entry for XHTML Basic This section contains the SGML Open Catalog-format definition of the XHTML Basic FPI. -- .......................................................................... -- -- File catalog ............................................................ -- -- XHTML Basic Catalog Data File Revision: $Id: xhtml-basic10.cat,v 2.4 2000/12/18 21:42:58 mimasa Exp $ SMI See "Entity Management", SGML Open Technical Resolution 9401 for detailed information on supplying and using catalog data. This document is available from OASIS at URL: -- -- .......................................................................... -- -- SGML declaration associated with XML .................................... -- OVERRIDE YES SGMLDECL "xml1.dcl" -- :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- -- XHTML Basic DTD modular driver file ..................................... -- PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN" "xhtml-basic10.dtd" -- XHTML Basic framework module ............................................. -- PUBLIC "-//W3C//ENTITIES XHTML Basic 1.0 Document Model 1.0//EN" "xhtml-basic10-model-1.mod" -- End of catalog data ..................................................... -- -- .......................................................................... -- B.2. XHTML Basic Driver This section contains the driver for the XHTML Basic document type implementation as an XML DTD. It relies upon XHTML module implementations defined in [XHTMLMOD]. %xhtml-framework.mod; %xhtml-text.mod; %xhtml-hypertext.mod; %xhtml-list.mod; %xhtml-image.mod;]]> %xhtml-table.mod;]]> %xhtml-form.mod;]]> %xhtml-link.mod;]]> %xhtml-meta.mod;]]> %xhtml-base.mod;]]> %xhtml-param.mod;]]> %xhtml-object.mod;]]> %xhtml-struct.mod; B.3. XHTML Basic Customizations An XHTML Family Document Type (such as XHTML Basic) must define the content model that it uses. This is done through a separate content model module that is instantiated by the XHTML Modular Framework. The content model module and the XHTML Basic Driver (above) work together to customize the module implementations to the document type's specific requirements. The content model module for XHTML Basic is defined below: