- From: Jan Richards <jan.richards@utoronto.ca>
- Date: Thu, 20 Aug 2009 08:06:49 -0400
- To: Henri Sivonen <hsivonen@iki.fi>
- CC: HTMLWG WG <public-html@w3.org>, W3C WAI-XTECH <wai-xtech@w3.org>
Hi Henri, Henri Sivonen wrote: > On Aug 19, 2009, at 23:43, Jan Richards wrote: > >>>>>> When used, a "missing" signal (however this might be encoded - as >>>>>> long as it is not in the @alt string) would communicate to the >>>>>> user agent that the @alt value should not be trusted. >>>>> What concretely is this envisioned to mean for user agent behavior? >>>> >>>> Since the semantic meaning would be "don't trust the @alt string" I >>>> would think the behaviour would be the same as it is now when @alt >>>> is fully missing. >>> This seems more problematic than a pure validator pragma. Why would a >>> generator generate an alt string and a signal for UAs to completely >>> ignore it? More importantly, having an "user agents should ignore alt >>> completely" marker would pose a backward and forward compatibility >>> problem: If the markup generator wants UAs to ignore the alt >>> completely, generating some alt and an "ignore" marker would make old >>> UAs not ignore the alt. If early adopters use the "ignore" marker >>> while testing in current UAs, future UAs would lose potentially >>> useful text alternatives. >> >> I can see the backwards compatibility problem, but not the forwards >> compatibility problem. Why would testers add the "ignore" marker while >> testing in current UAs? > > Given enough rope, Web authors do the wildest things for the craziest > reasons. However, here's a plausible non-crazy failure scenario: > > Author A creates a document using an authoring tool and fails to make > the document accessible. The authoring tool inserts the "ignore" marker. > Later, author B in author A's organization addresses the problem that > the document is inaccessible. Author B adds sensible alt text using a > text editor. While author B has read introductions to Web accessibility > to know about alt, author B isn't aware of the finer points of HTML > syntax and fails to remove the "ignore" marker. Now the document is > still inaccessible in UAs that honor the "ignore" marker. Author B could > even test the document in older UAs without noticing the problem. I see. Perhaps this could be addressed somewhat by advising authoring tools to automatically undo the "missing" mechanism if an author edits the @alt value. >>> If the user of the tool inserts an image (outside <figure>, etc. >>> special constructs) and doesn't provide a text alternative or rejects >>> (which must be an option under ATAG 2 B.2.4.2.a) a tool-suggested >>> text alternative but doesn't flag the image as omissible from AT >>> presentation, as far as I can tell, generating role=presentation >>> would be wrong by analogy with ATAG 2 B.2.4.4 and generating any alt >>> would be wrong per ATAG 2 B.2.4.3 when the tool has no relevant >>> sources that the UA wouldn't have. >> >> If the author rejects the suggested @alt value, ignores the >> prompts/checks for their own @alt, and turns off the "missing" >> mechanism then....yes, invalidity will result, but at some point, >> isn't that the author's choice? > > I meant in the absence of a "missing" mechanism. If a "missing" > mechanism is introduced, it makes no sense for authoring tools to have > UI for micromanaging the "missing" mechanism. Agreed. Cheers, Jan -- Jan Richards, M.Sc. User Interface Design Lead Adaptive Technology Resource Centre (ATRC) Faculty of Information University of Toronto Email: jan.richards@utoronto.ca Web: http://jan.atrc.utoronto.ca Phone: 416-946-7060 Fax: 416-971-2896
Received on Thursday, 20 August 2009 12:07:31 UTC