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Modularization proposals

From: Jason White <jasonw@ariel.ucs.unimelb.edu.au>
Date: Tue, 21 Aug 2001 11:31:43 +1000
Message-ID: <15233.47615.17457.974753@gargle.gargle.HOWL>
To: Web Content Guidelines <w3c-wai-gl@w3.org>
Without committing myself to any of these, I would like to summarize
the three aspects of "modularity" or "sectioning" which have been
considered in working group discussions, not only in recent threads
but also in earlier deliberations.

1. Modularity of the conformance scheme: it has sometimes been argued
   that (to use Charles McCathieNevile's helpful terminology)
   device-independence, interaction and navigation, and comprehension,
   respectively, should be treated as belonging to separate dimensions
   of conformance. It would thus be possible to make different
   conformance assertions with respect to each dimension. A precise
   proposal of this kind has not so far been formulated, but there are
   two obvious possibilities:

a. A two-way split, with device/modality-independence on the one side,
and interaction/navigation/comprehension on the other.

b. A three-way split, with device/modality-independence,
comprehension, and interaction/navigation, occupying separate
dimensions.

Such an approach need only affect the definition of conformance, though
it may of course be combined with proposals 2 and/or 3, below.

2. Organisation of the document: it has been suggested that the
   ordering and normative content of the guidelines should draw clear
   distinctions between the requirements related to
   modality/device-independence, interaction/navigation, and
   comprehension, respectively. Again, as in proposal 1, it would be
   possible to envisage a bipartite or a tripartite division of the
   material. Nevertheless, even if the guidelines were organised so as
   to provide a clear separation between modality/device-independence,
   interaction/navigation and comprehension, this would not
   necessarily preclude a unified conformance scheme. Consequently, it
   would be feasible to implement proposal 2 with or without proposal
   1.

3. Division into separate documents: This is an extension of proposal
   2, whereby each element would be treated in its own, individual
   document. If each such document were a separate Recommendation,
   then presumably it would be necessary to implement proposal 1 as
   well, since each Recommendation would be required to provide its
   own conformance scheme. Of course, it would be possible to regard
   all of the documents as a single Recommendation, with the
   separation being largely for the sake of convenience.

The role of the conformance definition in the guidelines has two
aspects:

1. Its primary purpose is to prescribe the information that must be
   provided by any content developer who wishes to make a claim
   regarding implementation of the guidelines. Thus, those who assert
   that they have implemented WCAG must specify the version of the
   document to which their claim refers, identify the web content to
   which it relates, and indicate which checkpoints have been
   satisfied.

2. The WCAG 1.0 conformance scheme also imposes a hierarchical
   structure upon conformance claims, based on checkpoint priorities,
   resulting in the "a", "double-a" and "tripple-a" levels. This
   aspect of the conformance system has been criticised on the basis
   that it discourages implementation of lower-priority checkpoints by
   developers who, for whatever reason, decide not to implement all of
   the checkpoints of higher priority. One solution which has been
   offered is to permit checkpoint-by-checkpoint claims of
   conformance, in which the developer enumerates the checkpoints
   which have been satisfied, for instance in RDF metadata. One could
   also say, for example, "Level double-a plus checkpoints x.x, y.y,
   ...".

Proposal 1, above, could perhaps be implemented by allowing two (or
three, depending on the nature of the split) types of conformance
assertion:

1. Device/modality-independence, at levels A, AA and AAA, defined
   according to checkpoint priorities as in WCAG 1.0.

2. Comprehension, at levels A, AA and AAA (or perhaps with a different
   measure of comprehensibility/required cognitive abilities of
   audience).

3. Interaction/navigation, at levels A, AA and AAA.

in addition to

4. Assertions regarding implementation of individual checkpoints.

The arguments which have been (and will probably continue to be)
raised against such a scheme is that it is complicated, and that it
fails to recognise the linkages between device/modality-independence,
on one hand, and interaction/navigation/comprehension on the other.
Advocates of such a conformance definition, however, will probably
argue that conformance determinations will increasingly be made with
the aid of evaluation tools, thus reducing the import of the
complexity argument. Also, it will probably be contended by some that
a compartmentalisation of the guidelines which distinguishes
device/modality-independence from interaction/navigation/comprehension
is not only feasible but also advantageous.

I hope this summary helps to clarify the issues and to inform further
discussion of these difficult and contentious topics.
Received on Monday, 20 August 2001 21:31:50 GMT

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