M. Baker The 'application/xhtml+xml' Media Type draft-baker-xhtml-media-reg-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 27, 2001. 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". 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-html@w3.org, a public mailing list with archives at . 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 HTML WG on XHTML Modularization (see http://www.w3.org/TR/xhtml-modularization), 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. As of December 2000, the HTML WG has taken no official position on what MIME media type should be used to describe XHTML 1.0 or any other XHTML based language, except in the case where XHTML 1.0 documents satisfy certain additional requirements (see [XHTML1] section 5.1) and can be described with "text/html" (see [TEXTHTML]). 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. The HTML WG expects to publish further documentation on this subject, including but not limited to, information about rules for which documents should and should not be described with this new media type, and further information about recognizing XHTML documents. 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]. 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]. schema-location 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, amoung 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. The HTML WG will be releasing further guidelines about what documents should and should not be described with this type. 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]. 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 preceeding 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", reflecting the fact that no applications currently recognize it. 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. File extension: There are two known file extensions that are currently in use for XHTML 1.0; ".xht" and ".xhtml". 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. Macintosh File Type code: TEXT Person & email address to contact for further information: Mark Baker 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 For documents labeled as "application/xhtml+xml", the fragment identifier notation is exactly that for application/xml, as specified in [XMLMIME]. 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. 5. Recognizing XHTML files All XHTML files will have the string " (or ). [MIME] Freed, N., and Borenstein, N., "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996. [XHTML1] "XHTML 1.0: The Extensible HyperText Markup Language: A Reformulation of HTML 4 in XML 1.0", W3C Recommendation, January 2000. Available at . [XML] "Extensible Markup Language (XML) 1.0", W3C Recommendation, February 1998. Available at (or ). [TEXTHTML] Connolly, D., Masinter, L., "The 'text/html' Media Type", RFC 2854, June 2000. [XMLMIME] Murata, M., St.Laurent, S., Kohn, D., "XML Media Types", Internet-Draft (work in progress). Available at .