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XHTML™-Print

Printer Working Group Draft, May 10, 2002

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Editors:
Don Wright, Lexmark International
Melinda Grant, HP
Peter Zehler, Xerox
Jun Fujisawa, Canon

 

Copyright © 2001-2002  Printer Working Group, All Rights Reserved.
XHTML is a trademark of the World Wide Web Consortium.

Abstract

HTML 4 is a powerful language for authoring Web content, but its design does not take into consideration issues pertinent to printers, including the implementation cost (in power, memory, etc.) of the full feature set. Printers have relatively limited resources that cannot generally afford to implement the full feature set of HTML 4.

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 print applications for a wide range of printers is difficult.

XHTML-Print's targeted usage is for printing in environments where it is not feasible or desirable to install a printer-specific driver and where some variability in the formatting of the output is acceptable.

The document type definition for XHTML-Print is implemented based on the XHTML modules 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 PWG.

This document is a draft and only a draft.  It has not been reviewed by PWG Members nor approved.  It is not a stable document and may not be used as reference material nor cited as a normative reference from another document.

Public discussion of XHTML-Print takes place on the mailing list: xp@pwg.org (archive). To subscribe send an email to majordomo@pwg.org with the words subscribe xp in the body.  You must be subscribed to the mailing list to post there.  Please report errors in this document to one of the editors listed above or on the mailing list.

A list of current PWG Standards and other technical documents can be found at http://www.pwg.org/standards.html

Table of Contents

1. Introduction

1.1. XHTML for Printing

This document specifies a simple XHTML based data stream suitable for printing as well as display. It is based on the W3C’s XHTML Basic with additional text and style treatments. Its targeted usage is for printing in environments where it is not feasible or desirable to install a printer-specific driver and where some variability in the formatting of the output is acceptable. Throughout this document this data stream is called “XHTML-Print.”

XHTML-Print is designed to be appropriate for low-cost printers that may not have a full-page buffer and that generally print from top-to-bottom and left-to-right with the paper in a portrait orientation. For other printers (i.e., those that print in another direction or orientation) a full-page buffer may be required.

XHTML-Print is not appropriate when strict layout consistency and repeatability across printers are required. The design objective of XHTML-Print is to provide a relatively simple, broadly supportable page description format where content preservation and reproduction are the goal, i.e. “Content is King.” Traditional printer page description formats such as PostScript or PCL are more suitable when strict layout control is required. XHTML-Print does not utilize bi-directional communications with the printer either for capabilities or status inquiries.

This document creates a set of conformance criteria for XHTML-Print. It provides a strong basis for rich printing results without a detailed understanding of each individual printer’s characteristics.

The document type definition for XHTML-Print is implemented based on the XHTML modules defined in Modularization of XHTML [XHTMLMOD].

1.2. Terminology

The keywords “MUST”, “SHALL”, “MUST NOT”, “SHALL NOT”, “REQUIRED”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” when used in this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification.

1.3. Design Rationale

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

1.3.1. Script and Events

The script and noscript elements are not supported as a printer lacks typical user interaction necessary for a script.  Content of the script should not be printed.

Event handler attributes used to invoke script programs are not supported. Events are device dependent and unlikely to happen in a printer. A generic event handling mechanism would be more appropriate than hardwiring the event names in the document type definition.

1.3.2. Presentation

Many simple printers cannot print a wide variety of fonts other than the generic serif, san serif and monospace. It is recommended that style sheets be used to create a presentation that is appropriate for a particular class of printer.

1.3.3. 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).

1.3.4. Tables

Basic XHTML tables ([XHTMLMOD], section 5.6.1) are supported, but tables can be difficult to format on very low resourced devices.  Note that in the Basic Tables Module, nesting of tables is prohibited.

1.3.5. Frames

Frames are not supported. Frames depend on a screen interface and therefore are not applicable to printers.

2. Conformance

This section is normative.

2.1. Document Conformance

A conforming XHTML-Print 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 validate against the DTD found in Appendix A and conform to the constraints expressed in Section 4.2.
  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 A using its Formal Public Identifier. The system identifier may be modified appropriately. 
    <!DOCTYPE html PUBLIC "-//PWG//DTD HTML-Print 1.0//EN"
"http://www.xhtml-print.org/xhtml-print/xhtml-print10.dtd">

2.2 Printer (User Agent) Conformance

2.2.1 Formatting/Rendering Rules

The printer user agent must conform to the "User Agent Conformance" section of the XHTML 1.0 specification ([XHTML1], section 3.2), subject to the following ammendments.

  1. Images:
    • If a printer encounters an image in a format it does not support, it shall render any alternate content provided in a supported format, and may reserve the space specified by the height and width attributes by optionally drawing a box around this space of the size specified for the image.
    • If the image format is not supported or the height and width attributes are absent and no alternate content is provided, the image may be omitted and no space reserved.
    • If the image format is supported and the height and width attributes were omitted, the printer may choose to omit the image from the page.
  2. If a printer encounters an element it does not recognize, it must render the element's content. However, printer user agents may chose not to render content within elements defined by XHTML, HTML or deprecated from HTML which is obviously not intended to be rendered, e.g. <script>.

       

      3. The XHTML-Print Document Type

      This section is normative.

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

      XHTML-Print 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
      Text Extension Module - Presentation**
      b, big, hr, i, small, sub, sup, tt
      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
      Style Sheet Module**
      style
      Link Module
      link
      Base Module
      base
      Object Module**
      object, param

      (*) = This module is a required XHTML Host Language module.
      (**) = These modules are not a part of XHTML Basic but are required for XHTML-Print.

      An XML 1.0 DTD is available in Appendix A.

      NOTE: Since the HTML event handler attributes are not included in XHTML-Print, form controls outside forms may not function as expected by the user.

      4. How to Use XHTML-Print

      This section is normative.

      XHTML-Print inherits all the structure, encoding and other basic infrastructure specified by XHTML. The following sections describe and clarify the application and usage restrictions of XHTML-Print.

      4.1 Recommended Attributes on the ‘img’ and ‘object’ Elements

      Because many printers create the page in a serial manner from top to bottom, it is important for the printer to know the size of images before retrieving the image data itself. This information is then used to create portions of the page layout.

      Therefore, the sender is strongly encouraged to include the height and width attributes either within the ‘img’ or the ‘object’ element, or within an associated style sheet rule. Printers may omit from the page images that do not include height and width attributes (see Section 6.3.1, item 4). These attributes may be expressed as percentages within the ‘img’ or the ‘object’ element, or may use the standard absolute or relative units within the CSS rule. Percentages are relative to the parent element and not the page width or printable area.

      4.2 Side-by-Side Images

      Low-cost printers today often have very little memory into which page data can be stored before being printed. As such, they must build and print the page in swaths on the fly from the top of the page to the bottom. The following guidelines maximize the capabilities of XHTML-Print in these lower cost printers.

      1. If two or more images will be even partially side-by-side on the printed page they should be included by reference (e.g., <img src="http://10.10.10.2/images/logo.jpg"> or <object data="http://10.10.10.2/images/logo.jpg">) rather than included in a compound document format such as application/vnd.pwg-multiplexed. This allows the printer to get chunks of the image, as it needs it, as it prints down the page.
      2. An XHTML-Print conforming printer lacking sufficient buffer space to hold multiple side-by-side images may choose to reformat the layout of the page to preserve content. Printers shall attempt to preserve content when encountering side-by-side images that may be impossible to print. Discarding the second and subsequent of the side-by-side images should be avoided unless preservation of content is best achieved by doing so. Other than attempting to best preserve content, this specification does not mandate any specific behavior when encountering this situation. Clients providing images inline should order them from left-to-right top-to-bottom unless the print direction is known to be otherwise.

      5. Acknowledgements

      This specification was prepared by the PWG XHTML-Print Working Group. The members were:

      • Don Wright, Lexmark
      • Melinda Grant, Hewlett-Packard
      • Jun Fujisawa, Canon
      • Peter Zehler, Xerox

       

      A. XHTML-Print DTD and Modules

      This appendix is normative.

      This section contains the pieces of the XHTML-Print DTD that are unique to XHTML-Print. The remaining entities and modules are as specified in reference [3].

      The following should be used from Modularization of XHTML [3]:

      1. xhtml-attribs-1.mod
      2. xhtml-base-1.mod
      3. xhtml-basic-form-1.mod
      4. xhtml-basic-table-1.mod
      5. xhtml-blkphras-1.mod
      6. xhtml-blkpres-1.mod
      7. xhtml-blkstruct-1.mod
      8. xhtml-charent-1.mod
      9. xhtml-datatypes-1.mod
      10. xhtml-framework-1.mod
      11. xhtml-hypertext-1.mod
      12. xhtml-image-1.mod
      13. xhtml-inlphras-1.mod
      14. xhtml-inlpres-1.mod
      15. xhtml-inlstruct-1.mod
      16. xhtml-inlstyle-1.mod
      17. xhtml-lat1.ent
      18. xhtml-link-1.mod
      19. xhtml-list-1.mod
      20. xhtml-meta-1.mod
      21. xhtml-notations-1.mod
      22. xhtml-object-1.mod
      23. xhtml-param-1.mod
      24. xhtml-pres-1.mod
      25. xhtml-qname-1.mod
      26. xhtml-special.ent
      27. xhtml-struct-1.mod
      28. xhtml-style-1.mod
      29. xhtml-symbol.ent
      30. xhtml-text-1.mod

      A.1. XHTML-Print 1.0 DTD

      <!-- ....................................................................... -->
<!-- XHTML-Print 1.0 DTD ................................................... -->
<!-- file: xhtml-print10.dtd
-->

<!-- XHTML-Print 1.0 DTD

     This is XHTML-Print 1.0, a variant of XHTML Basic for printing.

     Copyright 2001 Lexmark International Inc., Hewlett-Packard Company,
     Xerox Corporation, and Canon Inc. All Rights Reserved.

     Permission to use, copy, modify and distribute the XHTML-Print 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.

        Author:   Jun Fujisawa <fujisawa.jun@canon.co.jp>
        Revision: $Id: xhtml-print10.dtd,v 1.2 2001/06/04 17:16:35 fujisawa Exp $

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

     This DTD is identified by the PUBLIC and SYSTEM identifiers:

        PUBLIC "-//PWG//DTD XHTML-Print 1.0//EN"
        SYSTEM "http://www.xhtml-print.org/xhtml-print/xhtml-print10.dtd"
-->
<!ENTITY % XHTML.version "-//PWG//DTD XHTML-Print 1.0//EN" >

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

         "http://www.w3.org/1999/xhtml"
-->
<!ENTITY % NS.prefixed "IGNORE" >
<!ENTITY % XHTML.prefix "" >

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

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

<!-- Bidirectional Text features
     This feature-test entity is used to declare elements
     and attributes used for bidirectional text support.
-->
<!ENTITY % XHTML.bidi "IGNORE" >

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

<!ENTITY % xhtml-events.module "IGNORE" >
<!ENTITY % xhtml-bdo.module "%XHTML.bidi;" >

<!-- Style Attribute Module ............................ -->
<!ENTITY % xhtml-inlstyle.module "INCLUDE" >
<![%xhtml-inlstyle.module;[
<!ENTITY % xhtml-inlstyle.mod
     PUBLIC "-//W3C//ENTITIES XHTML Inline Style 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-inlstyle-1.mod" >
%xhtml-inlstyle.mod;]]>

<!-- Document Model Module ............................. -->
<!ENTITY % xhtml-model.mod
     PUBLIC "-//PWG//ENTITIES XHTML-Print 1.0 Document Model 1.0//EN"
            "xhtml-print10-model-1.mod" >

<!-- Modular Framework Module (required) ............... -->
<!ENTITY % xhtml-framework.mod
     PUBLIC "-//W3C//ENTITIES XHTML Modular Framework 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-framework-1.mod" >
%xhtml-framework.mod;

<!-- Text Module (required) ............................ -->
<!ENTITY % xhtml-text.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Text 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-text-1.mod" >
%xhtml-text.mod;

<!-- Hypertext Module (required) ....................... -->
<!ENTITY % xhtml-hypertext.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Hypertext 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-hypertext-1.mod" >
%xhtml-hypertext.mod;

<!-- Lists Module (required) ........................... -->
<!ENTITY % xhtml-list.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Lists 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-list-1.mod" >
%xhtml-list.mod;

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

<!-- Presentation Module ............................... -->
<!ENTITY % xhtml-pres.module "INCLUDE" >
<![%xhtml-pres.module;[
<!ENTITY % xhtml-pres.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Presentation 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-pres-1.mod" >
%xhtml-pres.mod;]]>

<!-- Image Module ...................................... -->
<!ENTITY % xhtml-image.module "INCLUDE" >
<![%xhtml-image.module;[
<!ENTITY % xhtml-image.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Images 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-image-1.mod" >
%xhtml-image.mod;]]>

<!-- Tables Module ..................................... -->
<!ENTITY % xhtml-table.module "INCLUDE" >
<![%xhtml-table.module;[
<!ENTITY % xhtml-table.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Basic Tables 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-basic-table-1.mod" >
%xhtml-table.mod;]]>

<!-- Forms Module ...................................... -->
<!ENTITY % xhtml-form.module "INCLUDE" >
<![%xhtml-form.module;[
<!ENTITY % xhtml-form.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Basic Forms 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-basic-form-1.mod" >
%xhtml-form.mod;]]>

<!-- Style Sheet Module ................................ -->
<!ENTITY % xhtml-style.module "INCLUDE" >
<![%xhtml-style.module;[
<!ENTITY % xhtml-style.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Style Sheets 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-style-1.mod" >
%xhtml-style.mod;]]>

<!-- Link Module ....................................... -->
<!ENTITY % xhtml-link.module "INCLUDE" >
<![%xhtml-link.module;[
<!ENTITY % xhtml-link.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Link Element 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-link-1.mod" >
%xhtml-link.mod;]]>

<!-- Metainformation Module ............................ -->
<!ENTITY % xhtml-meta.module "INCLUDE" >
<![%xhtml-meta.module;[
<!ENTITY % xhtml-meta.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Metainformation 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-meta-1.mod" >
%xhtml-meta.mod;]]>

<!-- Base Module ....................................... -->
<!ENTITY % xhtml-base.module "INCLUDE" >
<![%xhtml-base.module;[
<!ENTITY % xhtml-base.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Base Element 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-base-1.mod" >
%xhtml-base.mod;]]>

<!-- Param Module ...................................... -->
<!ENTITY % xhtml-param.module "INCLUDE" >
<![%xhtml-param.module;[
<!ENTITY % xhtml-param.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Param Element 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-param-1.mod" >
%xhtml-param.mod;]]>

<!-- Object Module ..................................... -->
<!ENTITY % xhtml-object.module "INCLUDE" >
<![%xhtml-object.module;[
<!ENTITY % xhtml-object.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Embedded Object 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-object-1.mod" >
%xhtml-object.mod;]]>

<!-- Structure Module (required) ....................... -->
<!ENTITY % xhtml-struct.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Document Structure 1.0//EN"
            "http://www.w3.org/TR/xhtml-modularization/DTD/xhtml-struct-1.mod" >
%xhtml-struct.mod;

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

      A.2. XHTML-Print 1.0 Document Model Module

      <!-- ....................................................................... -->
<!-- XHTML-Print 1.0 Document Model Module ................................. -->
<!-- file: xhtml-print10-model-1.mod

     This is XHTML-Print 1.0, a variant of XHTML Basic for printing.
     Copyright 2001 Lexmark International Inc., Hewlett-Packard Company,
     Xerox Corporation, and Canon Inc. All Rights Reserved.
     Revision: $Id: xhtml-print10-model-1.mod,v 1.2 2001/06/04 17:16:35 fujisawa Exp $

     This DTD module is identified by the PUBLIC and SYSTEM identifiers:

        PUBLIC "-//PWG//ENTITIES XHTML-Print 1.0 Document Model 1.0//EN"
        SYSTEM "http://www.xhtml-print.org/xhtml-print/xhtml-print10-model-1.mod

     ....................................................................... -->

<!-- XHTML-Print 1.0 Document Model

     This module describes the groupings of elements that make up
     common content models for XHTML-Print elements.
-->

<!-- Optional Elements in head ......................... -->

<!ENTITY % HeadOpts.mix
     "( %meta.qname; | %link.qname; | %object.qname; | %style.qname; )*" >

<!-- Miscellaneous Elements ............................ -->

<!ENTITY % Misc.class "" >

<!-- Inline Elements ................................... -->

<!ENTITY % InlStruct.class "%br.qname; | %span.qname;" >

<!ENTITY % InlPhras.class
     "| %em.qname; | %strong.qname; | %dfn.qname; | %code.qname;
      | %samp.qname; | %kbd.qname; | %var.qname; | %cite.qname;
      | %abbr.qname; | %acronym.qname; | %q.qname;" >

<!ENTITY % InlPres.class
     "| %tt.qname; | %i.qname; | %b.qname; | %big.qname;
      | %small.qname; | %sub.qname; | %sup.qname; " >

<!ENTITY % I18n.class "" >

<!ENTITY % Anchor.class "| %a.qname;" >

<!ENTITY % InlSpecial.class "| %img.qname; | %object.qname;" >

<!ENTITY % InlForm.class
     "| %input.qname; | %select.qname; | %textarea.qname;
      | %label.qname;"
>

<!ENTITY % Inline.extra "" >

<!ENTITY % Inline.class
     "%InlStruct.class;
      %InlPhras.class;
      %InlPres.class;
      %Anchor.class;
      %InlSpecial.class;
      %InlForm.class;
      %Inline.extra;"
>

<!ENTITY % InlNoAnchor.class
     "%InlStruct.class;
      %InlPhras.class;
      %InlPres.class;
      %InlSpecial.class;
      %InlForm.class;
      %Inline.extra;"
>

<!ENTITY % InlNoAnchor.mix
     "%InlNoAnchor.class;
      %Misc.class;"
>

<!ENTITY % Inline.mix
     "%Inline.class;
      %Misc.class;"
>

<!-- Block Elements .................................... -->

<!ENTITY % Heading.class
     "%h1.qname; | %h2.qname; | %h3.qname;
      | %h4.qname; | %h5.qname; | %h6.qname;"
>
<!ENTITY % List.class  "%ul.qname; | %ol.qname; | %dl.qname;" >

<!ENTITY % Table.class "| %table.qname;" >

<!ENTITY % Form.class  "| %form.qname;" >

<!ENTITY % BlkStruct.class "%p.qname; | %div.qname;" >

<!ENTITY % BlkPhras.class
     "| %pre.qname; | %blockquote.qname; | %address.qname;"
>

<!ENTITY % BlkPres.class "| %hr.qname;" >

<!ENTITY % BlkSpecial.class
     "%Table.class;
      %Form.class;"
>

<!ENTITY % Block.extra "" >

<!ENTITY % Block.class
     "%BlkStruct.class;
      %BlkPhras.class;
      %BlkPres.class;
      %BlkSpecial.class;
      %Block.extra;"
>

<!ENTITY % Block.mix
     "%Heading.class;
      | %List.class;
      | %Block.class;
      %Misc.class;"
>

<!-- All Content Elements .............................. -->

<!ENTITY % FlowNoTable.mix
     "%Heading.class;
      | %List.class;
      | %BlkStruct.class;
      %BlkPhras.class;
      %BlkPres.class;
      %Form.class;
      %Block.extra;
      | %Inline.class;
      %Misc.class;"
>

<!ENTITY % Flow.mix
     "%Heading.class;
      | %List.class;
      | %Block.class;
      | %Inline.class;
      %Misc.class;"
>

<!-- end of xhtml-print10-model-1.mod -->

      B. References

      B.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

      B.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