2.1.3 Content Negotiation (conneg)

NOTE: This charter is a snapshot of the 47th IETF Meeting in Adelaide, Australia. It may now be out-of-date. Last Modified: 03-Feb-00


E. Hardie <hardie@equinix.com>

Applications Area Director(s):

Keith Moore <moore@cs.utk.edu>
Patrik Faltstrom <paf@swip.net>

Applications Area Advisor:

Keith Moore <moore@cs.utk.edu>


A. Mutz <andy_mutz@hp.com>
G. Klyne <GK@ACM.ORG>

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Description of Working Group:

A number of Internet application protocols need to indicate recipient capabilities, characteristics, and preferences when the resources they handle can vary in form. This working group will finalize registration procedures for distinguishing attributes which cause the media delivered to vary in form. The registration of these "media features" will provide a supplement to the MIME registration of media types and enable the development of a cross-protocol vocabulary for exchanging information on recipient capabilities, characteristics, and preferences. Since these distinguishing attributes commonly occur in related sets, this working group will also describe at least one method for referring to composite media feature sets. Experimental methods for using these features and feature sets within specific protocol contexts may be developed within this group or within the groups standardizing the relevant protocols.

The working group is aware of applications which desire to negotiate what content is delivered as well as the form in which it is delivered. As much as possible, the group will endeavor to create a framework for exchange sturdy enough to handle the later addition of this type of negotiation. It will not, however, address this need directly nor will it limit its design choices based on the possible later addition of this negotiation.

Goals and Milestones:

Aug 99


Submission of W3C CCPP crosswalk to IESG for consideration as Informational

Aug 99


Submit Revised version of Content-Features draft

Aug 99


Submit Revised version of Composite Media Features

Sep 99


Submission of Type feature registration to IESG for consideration as a Proposed Standard.

Oct 99


Submission of Content-Features to IESG for consideration as a Proposed Standard.

Oct 99


Submission of Composite Media to IESG for consideration as a Proposed Standard.

Nov 99


Group enters FIN_WAIT


Request For Comments:







Media Features for Display, Print, and Fax



Media Feature Tag Registration Procedure



A Syntax for Describing Media Feature Sets



Protocol-independent content negotiation framework



Corrections to 'A syntax for describing media feature sets'

Current Meeting Report

Minutes for CONNEG for the 47th IETF.
Submitted by Ted Hardie, Chair
Reported by Geoff Horne

The group met Monday, March 27, 2000 from 7:30 to 9:30. This meeting should be the last meeting before the group closes down. CONNEG has only one milestone item to complete (short form representation of feature predicates); once it has completed that item, it will close.

The group first reviewed related work:

draft-hoffman-char-lang-media-02.txt (last call requested and expired)
draft-itef-fax-content-negotiation-01.txt (in early stages of completion)
draft-itef-rescap-proto-format-00.txt (may carry conneg data, but no requirements)
w3c CCPP (working on RDF-based system for capabiliti negotiation)
WAP UAPROF (input into CCPP and a format for client capability information within WAP)

Graham Klyne then reviewed comments from the IESG on the type feature and the content-features header proposals. There were no objections to the clarifications proposed. Only one substantive change is involved: where the type draft currently strongly discourages using parameters to MIME content-types listed in a type header, they now MUST NOT be included. Other changes to the draft included improved examples, which will be submitted in the revised draft to the IESG

Ned Freed pointed out that it would be useful to have a content type for media features, and he agree to write the document registering the type. He set a goal of March 31st, 2000 for the registration.

The group then reviewed the goals of the short form predicate proposals:

1) Do no harm. The current system works, but is chattier than it could be; this work is an optimizaiton and should be considered in that light.

2) Provide a method for using a short form to replace a number of features which occur in several alternate predicates.

3) Provide a short method for referencing a common feature grouping where there is a restricted set of such groupings such as occurs in the fax case.

4) Provide a common reference method for the short forms of feature predicates and the other feature types or values. This implies standardization on URIs, because of the u. features.

The group first discussed the common reference method issue and agreed that a URN-based reference for the registered features would be valuable. The group also agreed that this would be best accomplished in an IANA-wide registry and the chair agreed to discuss the matter with Michael Mealing and Leslie Daigle of the URN working group. [This discussion occurred later during the week and Michael Mealing agreed to write the documents necessary for creating an IANA URN name space).

The group then moved into a discussion of how to handle the short form issue for feature predicates. A lively debate ensued, with three examples from Graham Klyne providing the focus for several use cases. There was considerable confusion in the group present on the distinction between two different cases in which URLs figured as part of the auxillary predicate. During this discussion the document authors disagreed on the need for dereferencing in one of the cases, and one of the document authors withdrew support for cases in which dereferencing is necessary because the operational characteristics of that case were likely to be sub-optimal.

After a discussion period did not produce agreement among the group, the chair asked the document authors to take the in-line method upon which the group agreeed and seperate it into a different document. That document will be advanced to the IESG as a candidate for proposed standard. The document authors will revise the other two methods within a new document. The current plan would be to submit that work as an individual submission either at a later time or for experimental status now. Graham agreed to have the seperated draft to the working group for review by April 10, 2000 with a goal of working group review complete by April 30, 2000.


None received.