RE: REF 1.1a - Add definition to 1.1 for ability to be expressed in words

  > Date: Fri, 11 Jul 2003 09:30:36 -0500
  > From: "John M Slatin" <john_slatin@austin.utexas.edu>
  > To: <gv@trace.wisc.edu>, <w3c-wai-gl@w3.org>
  > Subject: RE: REF 1.1a - Add definition to 1.1 for ability to be expressed in  words
  > 
  > Gregg, the whole notion of "equivalence" is deeply problematic from any
  > kind of theoretical/philosophical standpoint (to say nothing of the
  > pragmatic issues!).  If we push it hard enough, there is no such thing
  > as a "text equivalent" for *any* non-text element-- and if you ask
  > people who do translation professionally (especially but not only
  > literary translation), there aren't even "text equivalents" for
  > *textual* elements.

I agree. But we should distinguish between criteria to assess
accessibility of the non-textual element and criteria to assess
conformance with respect to the checkpoint.

In my opinion it is easy to determine if the textual alternative is
equivalent: run a number of user tests, measure time to completion
and/or number of errors and then compare these results with results
obtained from a control group. (It's not a quick process,
but it is doable and if done properly it leads to repeatable results,
i.e. it is standard enough).

Therefore equivalent might mean "any user belonging to the specific
audience (like a deaf musician), in a specific situation (at home
using jaws x.y), can achieve a specified goal (understand, select,
distinguish, enjoy, buy, ...) with the same level of effectiveness,
productivity, satisfaction, security as any user that is not disabled
and that uses a graphical browser on her/his coloured screen.

On the other hand conformance requires that the webdeveloper can
assess the equivalence without having to resort to a sample of the
audience of the site.
What the webdeveloper has to check is a pseudo-equivalence as she/he
has to impersonate a range of disabled users, in a range of possible
situations (using jaws, homepage reader, lynx, a PDA browser, a wap
phone, ...), trying to perform the given goal with required levels of
effectiveness, efficiency, satisfaction and security.
I think that unless we (wcag WG) specify these ranges of users,
situations and the required levels so that they are concrete enough to
the "typical webdeveloper" then conformance to this checkpoint will
always be problematic, since it is heavily involved with content and
interpretation. 

Which is the main reason why this property (equivalency)
can be made machine testable only on very special cases (like ALTs for
spacers). 

        Giorgio Brajnik
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Received on Sunday, 13 July 2003 07:44:57 UTC