- From: Maurizio Boscarol <maurizio@usabile.it>
- Date: Thu, 10 Nov 2005 12:31:45 +0100
- To: "Bailey, Bruce" <Bruce.Bailey@ed.gov>
- CC: w3c-wai-gl@w3.org
Bailey, Bruce wrote: >>>22. The evidence is that the one-way statistical correlation >>>between sites that are valid to those that are accessible is >>>too overwhelming to be explained away by the hypotheses offered. >>> >>> > >MB: > > >>This is totally undemonstrated as far as we know. >> >> > >You are mistaken. The actual hypothesis is something like: "Paying attention to *only* validity results in highly accessible web sites." > > Who decided this is the actual hypotesis? It's not mine. I've already stated my hypotesis: "Validilty is a preliminary, necessary requirement to accessibility" We need to try to falsificate it. If we can't, we can hold the hypotesis. If we can falsify the hypotesis, then we can't accept it. This is how research is supposed to work, at least. Unfortunately, we already agree that the hypotesis is not always true, so we can't hold it. This is the hypotesis we discuss, this is what we have to decide whether to put in WCAG or not.. I think we're talking about different things. >http://lists.w3.org/Archives/Public/w3c-wai-ig/2000JanMar/0140.html > >AWK: > > >>The correlation may be caused if the careful, professional >>developers who choose to attend to validity are more likely to >>also attend to accessibility. >> >> > >That is a rational hypothesis but, in light of the observed experiential data, it must be regarded as an extraordinary claim requiring *some* evidence. > > We're definitively talking about different things. I could state that developers who attend to validity are more likely to attend to accessibility. Sure they are! This is because the places (forums, webistes, mailing lists) where we talk about accessibility we often also talk about validation and vice versa. And because wcag 1.0 already made the correlation between acc. and val. And because if one has the attitude to inform himself about rules, he is more likely to discover even more rules... This is so obvious that I can't talk about this a second more. But, again, it's not what I'm talking about. The point of my discussion is not if validation is or is not a best practice for web designer: it is. I strongly reccomend it. As a process, validation is extremely useful. But as a product quality, is validation necessary to have an accessible website? (see hyp. above) If we aren't able to distinguish "product standard" and "process standard", we're not walking a long way. As an example, ISO 13407 is a process standard: it explain how to develop things (using user centred design, in that case). ISO 9241 (and even ISO/IEC 9126) are product standard: they define the requirements products must have to reach a stated quality level. They talk about interface features, code quality, ando so on. In wcag maybe we are sometimes mixing up product and process. As a process (as I've already said in many other post), there are some practice that increase the probability to have a quality product. But Wcag will also be used as a testing methodology on product features. It will measure if a product is accessible, not (not only) how it has been made. Now the problem is: validaton is great automatic tool to develop and I use it as often as I can. But is any invalid site, at the end, really inaccessible? Well, we already agree that it's not always true. So, if it's not always true, it's not true as an absolute statement. We can't hold that statement. But, if we put validity at L1, our future test based on wcag 2.0 will conclude that every, even trivially, invalid pages and sites would be not accessible, even if they wouldn't be. This is the error we are now deciding to authorize. It's up to us, of course. The question then may be: how high is the risk of excluding accessible site from our L1 level test to be declared L1-compliant even for trivial (irrelevant for actual accessibility) errors of validity? If we think this risk is very low, we can forget it. But if the actual risk is a little higher than we think, we're making a low-power test from our set of guidelines. By "power of the test" I talk on the analogy of 1-beta (probability of 2nd type error) in statistical analysis. Just for the ones that know about it. We shouldn't forget that our WCAG will be used for a variety of different goals. Not only defining a quality process, but also to set up test tools, and a set of laws. Things changes, when you define a quality process and when you write mandatory legal requirement, or when measure the level of something. The problem that generate this discussion may be the mixing up product and process features, I suspect. Maurizio
Received on Thursday, 10 November 2005 11:19:02 UTC