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Re: validation for 508 (accessibility) compliance?

From: Jukka K. Korpela <jkorpela@cs.tut.fi>
Date: Mon, 28 Mar 2005 20:57:12 +0300 (EEST)
To: Bill Milbratz <bmilbratz@outstart.com>
Cc: www-validator@w3.org
Message-ID: <Pine.GSO.4.58.0503282051010.14491@korppi.cs.tut.fi>

On Mon, 28 Mar 2005, Bill Milbratz wrote:

> I haven't seen a '508' or 'html accessibility' dtd.

And you won't, since accessibility (and even the simplistic technical
rules that 508 is about) goes far beyond what can be expressed in a DTD.

For example, you _can_ say in a DTD that every <img> element must have an
alt attribute - but that's what current HTML DTDs say anyway. You _could_
similarly say that every <table> must have a summary attribute, but that
would be questionable. You cannot say that a <table> inside a <table> must
have a summary attribute, for example. Still less can you refer to "tables
with two or more logical levels of depth", which is a logical, not
syntactic concept. And you cannot say that <th> must be used for headers,
since there's no way to express such a requirement in a DTD. (Besides, the
requirement itself contradicts HTML specifications, which say that if a
cell acts both as a header and as data - whatever that means! - then <td>
should be used.)

There's not much you can do to improve current HTML DTDs to detect
accessibility problems. Requiring a lang attribute in <html> comes into my
mind.

-- 
Jukka "Yucca" Korpela, http://www.cs.tut.fi/~jkorpela/
Received on Monday, 28 March 2005 17:57:45 GMT

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