- From: Nick Kew <nick@webthing.com>
- Date: Fri, 8 Feb 2002 00:50:30 +0000 (GMT)
- To: Al Gilman <asgilman@iamdigex.net>
- cc: <w3c-wai-er-ig@w3.org>
On Thu, 7 Feb 2002, Al Gilman wrote: > [disclaimer -- this was written Tuesday. And this is a quick partial response to selected/specific points. > > The basic principle is that the "overall evaluation" question needs to be > answered by WCAG, not ER. Is that wai-wcag-editor? It doesn't exactly look lively. > >I've now used five levels: > > - Certain: we know this violates a guideline; no human check required. > > - High: A construct that is likely to be wrong, but we're not certain. > > - Medium: We can't tell; human checking required > > - Low: Something that's probably OK, but should be flagged for checking. > > - "-": Messages that definitely don't mean there's a problem. > > This last needs better definition. Why is there any event thrown? There was a very specific reason: pseudo-legalistic completeness in implementing Section508. The two messages that carry this weighting are: (1) A message in every document, saying "provide a text-only alternative if this fails to meet the criteria". (2) A message re clientside imagemaps, noting that valid HTML is sufficient to meet the guideline. Since Page Valet is a validator, no additional message is required for this section. > > > >In producing an overall document score, we simply evaluate the > >highest confidence warning anywhere in the document: > > > > - Certain => Fail > > - High => Probable Fail - check messages > > - Medium => Uncertain - check messages carefully! > > - Low => Probable Pass - check messages > > - '-' => Pass - no problems found > > > > It would be interesting to set quantitative targets for what the statistics > would be in an ideal world for these grades. Indeed it would. Do we have any volunteers? I fear if I undertook that work it might not be seen as an objective assessment. > But talking about the confidence levels inspires comparison with confidence > assessment practices in statistics or we sorta need to get quantitative or get > another word. > > >(unconditional pass is very hard indeed, but /WAI/ER/ scores it > >at WCAG single-A :-) > > I beg your pardon? There is no purely machinable way to arrive at a WCAG 1.0 > single-A assertion. It means the page doesn't trigger any WCAG single-A warnings. If you think it should, your comments will be welcome. > > > >Now, the Big Issue is assigning priorities. While the basic principle > >is to describe confidences, that is inevitably often subjective, > >and I'd really like some feedback on whether people agree with my > >assignments. > > Get Jim Ley to build you a spider and gather some data. I am running a spider, and have plenty of data. But again, if the tool reflects my prejudices (and includes PLACEHOLDER comments denoting something I already plan to improve on), then I'm not the right person to assess it. > "95% of the hit-weighted web content on the web that flunks this test flunks > in-depth manual assessment by the experts of the WCAG WG. So please give it > your careful attention." Ah, now that's interesting. Is there any existing corpus that has been manually assessed? There's clearly nothing specific to any one assessment tool in building such a corpus. > As Kynn has pointed out, a candidate warning nominated by the detection of > presentational attributes used in the HTML may be entirely pruned away by > checking for the presence of the CSS to "do it right." That's a higer-level > rollup that you can do off the logic of the checkpoint itself. I don't entirely agree with that, and will get round to responding at some point (if noone helps out with a followup I find easier to work with). -- Nick Kew Site Valet - the mark of Quality on the Web. <URL:http://valet.webthing.com/>
Received on Thursday, 7 February 2002 19:50:34 UTC