W3C home > Mailing lists > Public > w3c-wai-ig@w3.org > July to September 2008

RE: WCAG2 Conformance Questions

From: Peter Thiessen <peter.thiessen@primalfusion.com>
Date: Thu, 31 Jul 2008 20:22:31 +0100
To: Loretta Guarino Reid <lorettaguarino@google.com>
CC: "w3c-wai-ig@w3.org" <w3c-wai-ig@w3.org>, "public-comments-wcag20@w3.org" <public-comments-wcag20@w3.org>
Message-ID: <F208A763E9BAFE41BABD0D703938EB1724FFF64C19@MBX2.EXCHPROD.USA.NET>

Hello Loretta,

thanks for the detailed and helpful reply.


> Alt altributes are one of the ways of satisfying SC 1.1.1. However it
> is a complex success criterion. We have tried to cover the different
> options and situations in Understanding SC 1.1.1 at
> http://www.w3.org/WAI/GL/WCAG20/WD-UNDERSTANDING-WCAG20/text-equiv-all.html.
> Is there a situation where you are wondering whether to provide an alt
> attribute or use some other form of text alternative?

Right, the guideline "1.1.1 Non-text Content: All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below (Level A)" explicitly mentions audio and video in the description but does not mention images. I had to go digging for a reference to an image alt tag and only found one as a control image in a form, under "Additional information" > "For non-text content that is a control or accepts user input". Later on in the document textual alternatives are mentioned under "Specific Benefits of Success Criterion 1.1.1:" > "Text alternatives may help some people who have difficulty understanding the meaning of photographs, drawings". My opinion would be to explicitly mention image alt tags as close to the guideline definition/description as possible. Though I don't know much of the recent background context that went into the WCAG2 guidelines.


> The section of WCAG on "Statement of Partial Conformance" at
> http://www.w3.org/WAI/GL/WCAG20/#conformance-partial discusses two
> possibilities for aggregated content. Is there sufficient information
> there for you to determine which of the two options applies to your
> site?

I would say there is sufficient information and I was more so looking for a clever work around this. As a developer, I'm often looking for a hack if I'm told I can't do something <grin />.


> Can you tell us whether our definitions of flash (
> http://www.w3.org/WAI/GL/WCAG20/#flash-def ) and general flash and red
> flash thresholds (
> http://www.w3.org/WAI/GL/WCAG20/#general-thresholddef ) answer the
> question of what constitutes flash, and if not, what additional
> information is needed? Do the resources listed in Uhnderstanding 2.3.2
> ( http://www.w3.org/WAI/GL/WCAG20/WD-UNDERSTANDING-WCAG20-20080505/seizure-three-times.html
> ) help?

Working with the definition of a flash, I would say that moving content across the screen would not be considered a relative luminance change, and not a flash. I found the definition helpful but was left a bit uncertain but certain enough to say this requirement was met.


> "Data" in the handle for SC 3.3.4 refers to the clause "that modify or
> delete user-controllable data in data storage systems", where
> "user-controllable" is defined at
> http://www.w3.org/WAI/GL/WCAG20/#user-controllabledef . Is it clear
> from the definition whether your site manages user-controllable data?

Not really. From the definition of User controllable Data, it sounds like personal user information such as address information and perhaps preferences. This may clarify, would deleting a e-mail message, or deleting an element in a tree hierarchy containing definition terms through a Web interface be considered a user controllable data/action?


Also, for guideline "1.4.3 Contrast (Minimum)", to help determine the color ratio, a tool/calculator where a user can plug in RGB values would simplify the process/understanding; rather than only giving the formula ( http://www.w3.org/WAI/GL/WCAG20/WD-UNDERSTANDING-WCAG20-20080505/visual-audio-contrast-contrast.html#contrast-ratiodef). The time commitment to understand contrast ratios through the guidelines is rather high. A few example calculations would help, or at least help me <grin />. Would you or anyone have any example contrast calculations?


Regards
-peter
Received on Thursday, 31 July 2008 19:23:16 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 19 July 2011 18:14:28 GMT