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Re: validity.htm

From: Bjoern Hoehrmann <derhoermi@gmx.net>
Date: Wed, 09 Nov 2005 19:10:58 +0100
To: "Gregg Vanderheiden" <gv@trace.wisc.edu>
Cc: <w3c-wai-gl@w3.org>
Message-ID: <ag84n1pdqj4eo3g1chtqhju6v0lrt82ame@hive.bjoern.hoehrmann.de>

* Gregg Vanderheiden wrote:
>In prep for the discussion Thursday we have tried to compile all of the
>arguments pro and con as well as the suggested options from here.

You note that "validity" is not the same as "conformance" but you don't
actually say what it means in the context of the document. Very few W3C
specification actually define what it means for relevant content to be
"valid", and where they do (e.g., "Valid XML 1.0 document" and "Valid
CSS 2.1 style sheet") they vary greatly in what this entails.

WCAG 1.0 has a Priority 2 checkpoint "Create documents that validate to
published formal grammars." This is already a rather vague checkpoint;
e.g. in SVG 1.1 there is a formal grammar for the path syntax and there
is a DTD. Now, the DTD does not include the path syntax grammar and the
DTD is more restrictive than the conformance requirements due to limi-
tations of DTDs.

Another example is the integer data type used for some attributes,
"An <integer> is specified as an optional sign character ('+' or '-')
followed by one or more digits "0" to "9"." Is that a formal grammar?
Is the path syntax BNF? Is the DTD? Do you have to "validate against"
the SVG 1.1 DTD? With or without pre-processing of the document to avoid
"invalidating" conforming documents?

I also note that for HTML/XHTML it is a goal of the maintainers of the
W3C Markup Validator to check for all machine testable conformance
requirements rather than just for rules spelled out in the DTDs; if we
do this, and the relevant specifications don't change until then, this
will mean the vast majority of documents that currently pass it (which
as you know aren't many) will no longer pass. This includes e.g. the WAI
homepage http://www.w3.org/WAI/ which violates at least one subtle HTML
conformance requirement...

There are two things to consider here. Apparently there is some value in
allowing content providers to claim WCAG compliance. As people become
increasingly aware of web standards, sooner or later people will check
web sites claiming WCAG compliance in some Validator. It is likely that
this perceived discrepancy will reduce the value of WCAG compliance
claims, especially if the violated requirements are accessibility aids.

This would of course be easier to deal with without the all-or-nothing
conformance model...
-- 
Björn Höhrmann · mailto:bjoern@hoehrmann.de · http://bjoern.hoehrmann.de
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Received on Wednesday, 9 November 2005 18:10:44 GMT

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