W3C home > Mailing lists > Public > w3c-wai-gl@w3.org > July to September 2011

Re: some comments/questions on techniques instructions document for submitters

From: Detlev Fischer <fischer@dias.de>
Date: Fri, 19 Aug 2011 18:14:05 +0200
Message-ID: <4E4E8BCD.1050801@dias.de>
To: w3c-wai-gl@w3.org
Hi Tim Borland,

EVAL TF has just started so I went back to the level of atomic tests to 
see what their role might be in a practical accessibility evaluation 

  Atomic tests limited to a specific technique are certainly useful as a 
heuristic for implementers of such a technique to check whether they 
have implemented it correctly, and the points in the techniques 
instructions as well as your points on writing a 'good test' are 
therefore certainly valid on this level.

However, any evaluation procedure checking conformance of content to 
particular SC criteria needs to consider quite a number of techniques in 
conjunction. The 'complication' you mention can be avoided on the level 
of technique, not any longer on the level of SC.

Stating conformance to a particular SC  might involve a large number of 
techniques and failures, some applied alternatively, others in 
conjunction. For example, checking for compliance of all page content to 
SC 1.1.1 (Non-Text Content), any of the following 15 techniques and 
failures might be relevant: G95, G94, G100, G92, G74, G73, G196, H37, 
H67, H45, F67, F3, F20, F39, F65. And this does not even include the 
techniques which provide accessible text replacements for background images.

My belief is that in *practical terms*, concatenating a large number of 
partly interrelated atomic tests to arrive at a SC conformance judgement 
is just not a practical approach for human evaluation. If we want a 
*usable*, i.e., manageable procdure for a human tester to check whether 
the images on a page have proper alternative text, what *actually* 
happens is more something like a pattern matching of known (recogniszed) 

* Display all images together with alt text (and, where available, href)
* Scan for instances of known failures - this also needs
   checking the image context for cases like G74 and G196
* Render page with custom colours (images now disappear) and check
   whether text replacements for background images are displayed

Moreover, if the *severity* of failure needs to be reflected in the 
conformance claim or associated tolerance metrics, then the failure to 
provide alt text for a main navigation item or graphical submit button 
must not be treated the same way as the failure to provide alt on some 
supporter's logo in the footer of the page.

My point is that while I am all for precision, the requirements for a 
rather complex integrated human assessment of a multitude of techniques 
and failures practically rule out an atomic approach where each 
applicable test of each applicable technique is carried out sequentially 
along the steps provided and then processed according to the logical 
concatenation of techniques given in the "How to meet" document. It 
simpy would be far too cumbersome.

I realise that you have not maintained that evaluation should be done 
that way - I just took your thoughts as a starting point. We have only 
just started with the EVAL task force work - I am curious what solutions 
we will arrive at to ensure rigor and mappability while still coming up 
with a manageable, doable approach.


Am 05.08.2011 16:28, schrieb Boland Jr, Frederick E.:
> For
> http://www.w3.org/WAI/GL/wiki/Technique_Instructions
> General Comments:
> Under “Tests” should there be guidance on limiting the number of steps
> in a testing procedure (not making tests too involved)?
> (this gets to “what makes a good test”?
> In .. http://www.w3.org/QA/WG/2005/01/test-faq#good
> “A good test is:
>   * Mappable to the specification (you must know what portion of the
>     specification it tests)
>   * Atomic (tests a single feature rather than multiple features)
>   * Self-documenting (explains what it is testing and what output it
>     expects)
>   * Focused on the technology under test rather than on ancillary
>     technologies
>   * Correct “
> Does the information under “Tests” clearly convey information in these
> items to potential submitters?
> Furthermore, do we want to have some language somewhere in the
> instructions that submitted techniques should not be too “complicated”
> (should just demonstrate simple features or atomic actions if possible)?
> Editorial Comments:
> under “Techniques Writeup Checklist “UW2” should be expanded to
> “Understanding WCAG2”
> 3^rd bullet under “applicability” has lots of typos..
> Thanks and best wishes
> Tim Boland NIST

Detlev Fischer PhD
DIAS GmbH - Daten, Informationssysteme und Analysen im Sozialen
Geschäftsführung: Thomas Lilienthal, Michael Zapp

Telefon: +49-40-43 18 75-25
Mobile: +49-157 7-170 73 84
Fax: +49-40-43 18 75-19
E-Mail: fischer@dias.de

Anschrift: Schulterblatt 36, D-20357 Hamburg
Amtsgericht Hamburg HRB 58 167
Geschäftsführer: Thomas Lilienthal, Michael Zapp
Received on Friday, 19 August 2011 16:14:41 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 16 January 2018 15:34:08 UTC