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


5. Recognizing XHTML files

   All XHTML documents will have the string "<html" near the beginning
   of the document.  Some will also begin with an XML declaration which
   begins with "<?xml", though that alone does not indicate an XHTML
   document.  All conforming XHTML 1.0 documents will include an XML
   document type declaration with the root element type 'html'.

   XHTML Modularization provides a naming convention by which a public
   identifier for an external subset in the document type declaration of
   a conforming document will contain the string "//DTD XHTML".  And
   while some XHTML based languages require the doctype declaration to
   occur within documents of that type, such as XHTML 1.0, or XHTML
   Basic (http://www.w3.org/TR/xhtml-basic), it is not the case that all
   XHTML based languages will include it.

   All XHTML files should also include a declaration of the XHTML
   namespace.  This should appear shortly after the string "<html", and
   should read 'xmlns="http://www.w3.org/1999/xhtml"'.

6. Charset default rules

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

7. Security Considerations

   The considerations for "text/html" as specified in [TEXTHTML] and and
   for 'application/xml' as specified in [XMLMIME], also hold for
   'application/xhtml+xml'.

   In addition, because of the extensibility features for XHTML as
   provided by XHTML Modularization, it is possible that
   'application/xhtml+xml' may describe content that has security
   implications beyond those described here.  However, if the user agent
   follows the user agent conformance rules in [XHTML1], this content
   will be ignored.  Only in the case where the user agent recognizes
   and processes the additional content, or where further processing of
   that content is dispatched to other processors, would security issues
   potentially arise.  And in that case, they would fall outside the
   domain of this registration document.









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


8. The "profile" optional parameter

   This parameter is meant to solve the short-term problem of using MIME
   media type based content negotiation (such as that done with the HTTP
   "Accept" header) to negotiate for a variety of XHTML based languages.
   It is intended to be used only during content negotiation.  It is not
   expected that it be used to deliver content, or that origin web
   servers have any knowledge of it (though they are welcome to).  It is
   primarily targeted for use on the network by proxies in the HTTP
   chain that manipulate data formats (such as transcoders).

   The parameter is intended to closely match the semantics of the
   "profile" attribute of the HEAD element as defined in [HTML401]
   (section 7.4.4.3), except it is applied to the document as a whole
   rather than just the META elements.  More specifically, the value of
   the profile attribute is a URI that can be used as a name to identify
   a language.  Though the URI need not be resolved in order to be
   useful as a name, it could be a namespace, schema, or a language
   specification.

   As an example, user agents supporting only XHTML Basic (see
   http://www.w3.org/TR/xhtml-basic) currently have no standard means to
   convey their inability to support the additional functionality in
   XHTML 1.0 [XHTML1] that is not found in XHTML Basic.  While XHTML
   Basic user agent conformance rules (which are identical to XHTML 1.0)
   provide some guidance to its user agent implementators for handling
   some additional content, the additional content in XHTML 1.0 that is
   not part of XHTML Basic is substantial, making those conformance
   rules insufficient for practical processing and rendering to the end
   user.  There is also the matter of the potentially substantial burden
   on the user agent in receiving and parsing this additional content.

   The functionality afforded by this parameter can also be achieved
   with at least two other more general content description frameworks;
   the "Content-features" MIME header described in RFC 2912, and UAPROF
   from the WAPforum (see http://www.wapforum.org/what/technical.htm).
   At this time, choosing one of these solutions would require excluding
   the other, as interoperability between the two has not been defined.
   For this reason, it is suggested that this parameter be used until
   such time as that issue has been addressed.

   An example use of this parameter as part of a HTTP GET transaction
   would be;

      Accept: application/xhtml+xml;
        profile="http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"





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9. Author's Address

   Mark A. Baker
   Planetfred, Inc.
   44 Byward Market, Suite 240
   Ottawa, Ontario, CANADA. K1N 7A2
   Phone: [phone]
   EMail: [e-mail]
   EMail: [e-mail]

   Peter Stark
   Ericsson Mobile Communications
   Phone: [phone]
   EMail: [e-mail]

10.  References

   [HTML401]   Raggett, D., et al., "HTML 4.01 Specification", W3C
               Recommendation. Available at
               <http://www.w3.org/TR/html401> (or
               <http://www.w3.org/TR/1999/REC-html401-19991224>).

   [MIME]      Freed, N. and N. Borenstein, "Multipurpose Internet Mail
               Extensions (MIME) Part Two: Media Types", RFC 2046,
               November 1996.

   [URI]       Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
               Resource Identifiers (URI): Generic Syntax", RFC 2396,
               August 1998.

   [XHTML1]    "XHTML 1.0: The Extensible HyperText Markup Language: A
               Reformulation of HTML 4 in XML 1.0", W3C Recommendation.
               Available at <http://www.w3.org/TR/xhtml1>.

   [XML]       "Extensible Markup Language (XML) 1.0", W3C
               Recommendation.  Available at <http://www.w3.org/TR/REC-
               xml> (or <http://www.w3.org/TR/2000/REC-xml-20001006>).

   [TEXTHTML]  Connolly, D. and L. Masinter, "The 'text/html' Media
               Type", RFC 2854, June 2000.

   [XMLMIME]   Murata, M., St.Laurent, S. and D. Kohn, "XML Media
               Types", RFC 3023, January 2001.

   [XHTMLM12N] "Modularization of XHTML", W3C Recommendation. Available
               at: <http://www.w3.org/TR/xhtml-modularization>





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11.  Full Copyright Statement

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

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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