Mapping between URIs and Internet Media Types

TAG Finding 8 April 2002 (Revised 27 May 2002)

This version:
Stuart Williams


The question (see issue uriMediaType-9) that prompted this finding was "Why does the Web use Internet media types and not URIs?" This finding documents the TAG's opinion on the relationship between URIs and Internet Media Types and proposes the establishment of a single, normative recommendation for mapping between Internet media types [RFC2046] and URI [RFC2396].

Status of this document

This document has been produced by the W3C Technical Architecture Group (TAG). The TAG approved this finding at its 8 April 2002 teleconference. At their 16 Dec 2002 teleconference, the TAG agreed to add a publication date to this document, consistent with the TAG's expectation that findings no longer be modified in place.

Additional TAG findings, both approved and in draft state, may also be available. The TAG expects to incorporate this and other findings into a Web Architecture Document that will be published according to the process of the W3C Recommendation Track.

Please send comments on this finding to the publicly archived TAG mailing list www-tag@w3.org (archive).

1. Relevant Principles of Web Architecture

2. Related Work

The W3C TAG is aware of:

  1. A mapping between Internet media types and URI's under a new Content-Type: URI scheme by Donald Eastlake [Eastlake]
  2. A scheme for assiging URN's to important IETF protocol parameters including Internet media types by the IETF Network Working Group [Iana-Urn] .

3. Mapping between Internet Media Types and URIs

The TAG regards Internet media types to be important resources that deserve identification by URI.

Both Internet media types and URIs are used in various contexts for document type labeling. The TAG supports the establishment of a single, normative recommendation for mapping between Internet media types [RFC2046] and URIs [RFC2396].

The TAG has a strong preference that URIs resulting from this mapping be dereferenceable. The TAG requests that IANA, the authority which adminsters the registry of Internet media types, be committed to providing persistent and dereferencable URIs that return a document containing human and/or machine readable information about the associated Internet media type, including references to other sources of human readable and machine readable documentation.

Eastlake proposes a mapping to a new URI scheme, "Content-Type:", for which there is no resolution or dereference mechanism, specified or deployed. The IETF Network Working Group propose a mapping to URNs, which, in general, cannot be dereferenced.

The TAG would prefer that dereferencable http: scheme URIs be assigned under the authority of the body that maintains the Internet media type registry.


"Mapping Between MIME Types, Content-Types, and URIs", Eastlake, D., Internet Draft. Located at http://www.ietf.org/internet-drafts/draft-eastlake-cturi-03.txt.
"An IETF URN Sub-namespace for Registered Protocol Parameters", Mealling, M. et al., IETF Network Working Group, Internet Draft. Located at http://www.ietf.org/internet-drafts/draft-mealling-iana-urn-02.txt.
"Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", Freed, N. et. al, IETF Network Working Group, RFC 2046. Located at http://www.ietf.org/rfc/rfc2046.txt.
"Uniform Resource Identifiers (URI): Generic Syntax", Berners-Lee, T. et al, IETF Network Working Group, RFC 2396. Located at http://www.ietf.org/rfc/rfc2396.txt.

Last modified: $Date: 2010/06/03 19:29:13 $