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Re: WCAG formalization (rewriting WCAG HTML techniques as automatable rules)

From: David Woolley <david@djwhome.demon.co.uk>
Date: Sat, 28 May 2005 16:26:05 +0100 (BST)
Message-Id: <200505281526.j4SFQ5h11109@djwhome.demon.co.uk>
To: w3c-wai-ig@w3.org

> In order to have better WCAG rules for automated tools, I recently
> published [1]. They are just a set of XPath/XQuery based expressions that
> rewrite WCAG in a more automatable and less fuzzy way.

They don't just rewrite, but they weaken.  The rules need to be somewhat
fuzzy because one needs human intelligence to apply them properly.

You say that certain things are required for XHTML, implying they are
not required for HTML, but most HTML is at least HTML 4.01, even if
it fails to include the necessary doctype, so alt attributes are already
required.  I am pretty sure that title is mandatory in all versions of
HTML (the head element is also mandatory, although both opening and
closing tags can be left out).

The two cases of meta refresh are explained by the following note in
the guidelines:

   Editorial Note: MC: I think we should clearly separate out the
   "surprise" problem from the misuse of meta problem, which isn't
   actually a violation.

Using it for redirection is an abuse, which is noted in the HTML 
specification itself.

I disagree that most authors would prefer to let the platform choose
relative sizes.  Most commercial authors don't like relative sizes at
all!

alt attributes neither describe the image nor describe its function; they
replace the function.  E.g in an example I saw recently, which probably
doesn't have alt text, an image of a chevron ">>" should have an alt
attribute of "to" if the image is used to separate source and destination 
or the lower and upper bounds of a range.  It should not be "image of 
chevron arrow" or "used to separate the two ends of a range".

display: hidden should be visibility: hidden

The reason that you cannot use @media for skip links is that current 
AT generally considers itself to be using the screen media type.

Any currently unused, non-reserved, target name will cause a pop-up, not
just _blank or _new.  They can also cause pop-unders if used but not in
the current frameset.

alt text needs to be short because it is expected to be comprehended by the
user in not much more time than someone viewing visually and familiar with
any graphic conventions used.

As typically used, HTML doesn't really have image buttons.  I don't believe
it is possible to automatically distinguish them from image mapped form
controls, although those also need an accessibility fall back.
Received on Saturday, 28 May 2005 15:31:10 GMT

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