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Re: RE: working definition of baseline

From: Jason White <jasonw@ariel.its.unimelb.edu.au>
Date: Sat, 7 May 2005 13:28:37 +1000
Message-ID: <17020.13797.909305.156081@jdc.local>
To: Web Content Guidelines <w3c-wai-gl@w3.org>

lguarino@adobe.com writes:
 > Ah, I see we do have different understandings of "baseline".
 > I was trying to define "baseline" as a reflection of the state of user 
 > agent technology, to provide guidance to authors about what 
 > technologies they could draw on and still hope to produce accessible 
 > content.
 > You appear to define "baseline" on a per-site basis, as the list of 
 > technologies your user agent needs to support to access a particular 
 > instance of web content. I think you are trying to provide guidance to 
 > users.

I agree there are important differences here that need to be worked
out. I wasn't intending the concept of baseline to provide guidance to
anybody. Rather, the baseline is chosen by the author according to
decisions made about which technologies it is reasonable to rely on in
designing the content, taking into account the user agents likely to
be available to users, accessibility requirements, and other relevant

In most circumstances this will be easy to do, as a policy-maker, or
this working group in the case of baselines provided in techniques as
suggestions, will have carried out the background work of deciding
what baseline is appropriate.

Next, an instance of Web content is written in accordance with the
baseline that the author has chosen: the content relies on all the
technologies specified in the baseline, and the declaration associated
with the conformance statement reflects this.

The central idea is that a baseline is descriptive, not normative; it
tells you which technologies a Web site or other piece of content
depends on.

Now suppose the author decides to add more content within the scope of
the conformance claim, but the new content requires a technology not
listed in the baseline. Now the original baseline is inaccurate and
has to be updated to include the extra technology, because there is
now content in the scope of the conformance claim that requires it.

Likewise, if we decide to evaluate a conformance claim, we assess
whether the content meets the relevant WCAG success criteria using
techniques appropriate to the baseline that the author has declared,
as well as the other technologies that the content makes use of but
does not depend on, and which are therefore not in the baseline.

The guidance we provide in techniques and elsewhere helps authors to
choose baselines; the baselines themselves are not guidance - they're
accurate descriptions of the assumptions that the author has chosen to
make in designing all the content covered by a particular conformance

I hope this at least helps to elucidate my earlier e-mail.
Received on Saturday, 7 May 2005 03:29:31 UTC

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