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Proposed structure for media-dependent conformance

From: Ian Jacobs <ij@w3.org>
Date: Wed, 16 Dec 1998 14:26:39 -0500
Message-ID: <3678096F.177FEEE8@w3.org>
To: w3c-wai-ua@w3.org

As per my action item in today's teleconf (raw minutes available
at [1]), here is a proposed structure for how UAs can claim
media-dependent conformance:

1) The document lists a finite number of "media types", based on, but
   not limited to, those defined by the CSS2 specification [2].

2) In the guidelines document, each media type is defined (only) as a
   of priority 1 techniques. Thus, for example, the "tty" media type
   (or perhaps the term should be "UA type") might include 13
   techniques, to be selected by the WG. The "handheld" media
   type might include 17 other techniques. A media type thus 
   establishes a subset of Priority 1 techniques to which a 
   UA may claim conformance.

3) Note that this eliminates any English language description
   of what a User Agent must do to qualify as rendering to
   a given media type. An English language description will
   necessarily be incomplete and should not be used for
   measuring conformance. Conformance will simply be to a 
   subset of Pri 1 techniques as chosen by the Working Group.
   We should also include <em>informative</em> text about
   what the WG had in mind when defining the media types,
   but the definition only is about a subset of techniques.

The goal of this proposal is to allow (force)
the UA Working Group to specify coherent subsets
required for conformance rather than allowing (or forcing)
User Agent developers to decide which techniques it feels are 
important to implement. 

Charles McCathieNeville has expressed concern that the WG,
by choosing subsets, will make conformance difficult for some
User Agents that can't implement all the techniques in that

I propose, therefore, a "core" set of Pri 1 techniques that 
must be implemented by all User Agents. Thus, a User Agent not able to
implement a larger subset of the techniques would
at least have to conform to the core subset. 

In addition, we might add a clause to the effect that
in addition to the core subset, UAs must implement those
techniques relating to what they do (e.g., any UA that
does sound has to do the techniques related to sound) and
common sense will be the measure of which techniques are
appropriate. I feel that leaving that choice to the UA
weakens the definition of conformance, however, and I prefer
just defining a "core" subset.

All comments about this proposal are welcome,

 - Ian

[1] http://www.w3.org/WAI/UA/1998/12/wai-ua-telecon-19981216.txt
[2] http://www.w3.org/TR/REC-CSS2/media.html
Ian Jacobs (jacobs@w3.org) 
Tel/Fax: (212) 684-1814 
Received on Wednesday, 16 December 1998 14:27:00 UTC

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