Conformance dimension: technology support

As discussed at today's teleconference, a frequently recurring issue
in this working group is that of how to address the changing
capabilities of user agents and other software within the framework of
the guidelines. To appreciate the full context of this proposal I
suggest reading the minutes of today's meeting.

Disclaimer: the following proposal is put forward as an idea for
discussion; it does not necessarily have my personal or unqualified
support. Nevertheless, elements of it have appeared in working group
meetings from time to time. As I remember, Matt was one of the first
to suggest it at a teleconference last year. Nevertheless, here is an
attempt to crystallize the ideas as a concrete proposal.

The essence of the proposal is that the conformance scheme for WCAG
2.0 would incorporate a distinction between what I shall here call
"semantic" and "operational" conformance. These may be characterized
as types or levels of conformance that apply to the techniques and/or
(possibly) the success criteria under each checkpoint. Thus, these
conformance types do not distinguish between checkpoints; they only
designate the way in which each checkpoint with respect to which a
conformance assertion has been made, is implemented.

1. Each checkpoint specifies an access requirement which, if met, will
   make the content more accessible to one or more groups of users.
   These are functional, end-user, requirements.

2. Semantic conformance is reached if the necessary information is
   provided, for example in markup or a data model, to allow a tool to
   satisfy the relevant end-user need reliably. The test of
   reliability is that a well understood, practically implementable,
   deterministic method exists whereby this information can be
   extracted and processed in software so as to satisfy the end-user
   need. By deterministic we mean that the method does not rely on
   heuristics or probabilistic analysis, but is guaranteed to give
   accurate results. By "implementable" we mean that it has actually
   been implemented in tools, or that it relies on techniques and
   algorithms which are widely understood and are regarded as amenable
   to implementation in the proposed context.

3. Operational conformance is reached if the content is so designed
   that the end-user requirement expressed in the checkpoint has been
   met using techniques which are well supported by user agents,
   assistive technologies or other applicable software. By "well
   supported" we mean that the pertinent technologies and features
   have been implemented and available in relevant software for a
   significant period of time (the exact time period would need to be
   specified more precisely), are available in
   internationalized/localized versions of such software, and do not
   exhibit serious interoperability problems that would preclude
   implementation by content authors. These requirements can of course
   be fine-tuned.

This conformance proposal would affect our work in at least the
following areas:

a. In the techniques documents, individual techniques would be labeled
as satisfying the "semantic" or "operational" conformance levels
(possibly both). In the case of techniques which are claimed to allow
implementation of a checkpoint at an operational level (see the
foregoing definition), the working group would require that testing
have been carried out to show that the technique is practically useful
and supported by user agents/assistive technologies.

Details of which techniques were relevant to the "semantic" or
"operational" conformance levels, would change over time as new tools
were released and existing software updated. Thus, whenever the
techniques documents were revised, the label associated with each
technique would need to be reconsidered in view of the state of
deployed technology at the time.

b. In our success criteria, the situation is somewhat more
problematic. We could either (1) maintain the generic nature of the
guidelines by stating the success criteria in terms that do not depend
on particular methods of implementation that are likely to change as
technology evolves; or (2) specify each of the available approaches as
alternatives in the success criteria, then provide guidance in the
techniques documents as to which solutions would entitle a developer
to claim "semantic" conformance, and which would justify an assertion
of "operational" conformance. Both of these potential approaches would
be compatible with our goal of keeping "until user agents"
qualifications out of the guidelines document itself.

c. In our conformance scheme, we would allow conformance claims to
specify whether the content met the relevant checkpoints at the
"semantic" or "operational" level.

Note: one consequence of this proposal is that content developers
would not need to consider the subtleties of the distinction between
"semantic" and "operational" conformance, since the specifics
regarding which techniques counted toward the satisfaction of each of
these conformance types, would be prescribed by the working group and
stated explicitly in the techniques documents. In effect, the task of
determining whether "until user agents" requirements had been met,
would be primarily the responsibility of the working group, to be
carried out as part of the task of writing and revising the techniques
document corresponding to each technology (in contrast with having a
separate "user agent support" page).

Received on Thursday, 14 March 2002 19:05:47 UTC