rfc3236.txt

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Network Working Group                                           M. Baker
Request for Comments: 3236                              Planetfred, Inc.
Category: Informational                                         P. Stark
                                          Ericsson Mobile Communications
                                                            January 2002


                 The 'application/xhtml+xml' Media Type

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document defines the 'application/xhtml+xml' MIME media type for
   XHTML based markup languages; it is not intended to obsolete any
   previous IETF documents, in particular RFC 2854 which registers
   'text/html'.

1. Introduction

   In 1998, the W3C HTML working group began work on reformulating HTML
   in terms of XML 1.0 [XML] and XML Namespaces [XMLNS].  The first part
   of that work concluded in January 2000 with the publication of the
   XHTML 1.0 Recommendation [XHTML1], the reformulation for HTML 4.01
   [HTML401].

   Work continues in the Modularization of XHTML Recommendation
   [XHTMLM12N], the decomposition of XHTML 1.0 into modules that can be
   used to compose new XHTML based languages, plus a framework for
   supporting this composition.

   This document only registers a new MIME media type,
   'application/xhtml+xml'.  It does not define anything more than is
   required to perform this registration.









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RFC 3236         The 'application/xhtml+xml' Media Type     January 2002


   This document follows the convention set out in [XMLMIME] for the
   MIME subtype name; attaching the suffix "+xml" to denote that the
   entity being described conforms to the XML syntax as defined in XML
   1.0 [XML].

   This document was prepared by members of the W3C HTML working group
   based on the structure, and some of the content, of RFC 2854, the
   registration of 'text/html'.  Please send comments to www-
   [e-mail], a public mailing list (requiring subscription) with
   archives at <http://lists.w3.org/Archives/Public/www-html/>.

2. Registration of MIME media type application/xhtml+xml

    MIME media type name:      application
    MIME subtype name:         xhtml+xml
    Required parameters:       none
    Optional parameters:

      charset
         This parameter has identical semantics to the charset parameter
         of the "application/xml" media type as specified in [XMLMIME].

      profile
         See Section 8 of this document.

   Encoding considerations:
      See Section 4 of this document.

   Security considerations:
      See Section 7 of this document.

   Interoperability considerations:
      XHTML 1.0 [XHTML10] specifies user agent conformance rules that
      dictate behaviour that must be followed when dealing with, among
      other things, unrecognized elements.

      With respect to XHTML Modularization [XHTMLMOD] and the existence
      of XHTML based languages (referred to as XHTML family members)
      that are not XHTML 1.0 conformant languages, it is possible that
      'application/xhtml+xml' may be used to describe some of these
      documents.  However, it should suffice for now for the purposes of
      interoperability that user agents accepting
      'application/xhtml+xml' content use the user agent conformance
      rules in [XHTML1].







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RFC 3236         The 'application/xhtml+xml' Media Type     January 2002


      Although conformant 'application/xhtml+xml' interpreters can
      expect that content received is well-formed XML (as defined in
      [XML]), it cannot be guaranteed that the content is valid XHTML
      (as defined in [XHTML1]).  This is in large part due to the
      reasons in the preceding paragraph.

   Published specification:
      XHTML 1.0 is now defined by W3C Recommendation; the latest
      published version is [XHTML1].  It provides for the description of
      some types of conformant content as "text/html", but also doesn't
      disallow the use with other content types (effectively allowing
      for the possibility of this new type).

   Applications which use this media type:
      Some content authors have already begun hand and tool authoring on
      the Web with XHTML 1.0.  However that content is currently
      described as "text/html", allowing existing Web browsers to
      process it without reconfiguration for a new media type.

      There is no experimental, vendor specific, or personal tree
      predecessor to 'application/xhtml+xml'.  This new type is being
      registered in order to allow for the expected deployment of XHTML
      on the World Wide Web, as a first class XML application where
      authors can expect that user agents are conformant XML 1.0 [XML]
      processors.

   Additional information:

      Magic number:
         There is no single initial byte sequence that is always present
         for XHTML files.  However, Section 5 below gives some
         guidelines for recognizing XHTML files. See also section 3.1 in
         [XMLMIME].

      File extension:
         There are three known file extensions that are currently in use
         for XHTML 1.0; ".xht", ".xhtml", and ".html".

         It is not recommended that the ".xml" extension (defined in
         [XMLMIME]) be used, as web servers may be configured to
         distribute such content as type "text/xml" or
         "application/xml".  [XMLMIME] discusses the unreliability of
         this approach in section 3.  Of course, should the author
         desire this behaviour, then the ".xml" extension can be used.







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RFC 3236         The 'application/xhtml+xml' Media Type     January 2002


      Macintosh File Type code: TEXT

   Person & email address to contact for further information:
      Mark Baker <[e-mail]>

   Intended usage: COMMON

   Author/Change controller:
      The XHTML specifications are a work product of the World Wide Web
      Consortium's HTML Working Group.  The W3C has change control over
      these specifications.

3. Fragment identifiers

   URI references (Uniform Resource Identifiers, see [RFC2396] as
   updated by [RFC2732]) may contain additional reference information,
   identifying a certain portion of the resource. These URI references
   end with a number sign ("#") followed by an identifier for this
   portion (called the "fragment identifier"). Interpretation of
   fragment identifiers is dependent on the media type of the retrieval
   result.

   For documents labeled as 'text/html', [RFC2854] specified that the
   fragment identifier designates the correspondingly named element,
   these were identified by either a unique id attribute or a name
   attribute for some elements. For documents described with the
   application/xhtml+xml media type, fragment identifiers share the same
   syntax and semantics with other XML documents, see [XMLMIME], section
   5.

   At the time of writing, [XMLMIME] does not define syntax and
   semantics of fragment identifiers, but refers to "XML Pointer
   Language (XPointer)" for a future XML fragment identification
   mechanism. The current specification for XPointer is available at
   http://www.w3.org/TR/xptr. Until [XMLMIME] gets updated, fragment
   identifiers for XHTML documents designate the element with the
   corresponding ID attribute value (see [XML] section 3.3.1); any XHTML
   element with the "id" attribute.

4. Encoding considerations

   By virtue of XHTML content being XML, it has the same considerations
   when sent as 'application/xhtml+xml' as does XML.  See [XMLMIME],
   section 3.2.







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