- From: Judy Brewer <jbrewer@w3.org>
- Date: Mon, 25 Apr 2011 13:18:57 -0400
- To: HTML Accessibility Task Force <public-html-a11y@w3.org>
Note that based on the discussion today http://www.w3.org/2011/04/25-text-minutes.html some of the items and the content in the response below will be changing. Summary as of the end of today's "Text Alternatives Sub-Group" call include, with respect to the six sub-decisions on validation of alt: - aria-labelledby -- leave as is (no response) - role=presentation -- Rich & Steve discussing, will propose text to the list - meta name=generator -- John drafting (with Leif? Judy invite) - private communications -- leave as is (no response) - title -- Steve and Geoff will each propose additional content - figcaption -- Geoff & Judy discussing, will propose text to the list We're looking for responses on these by mid-week, so that we can prepare a comprehensive clarification email by Friday that the Text Alternatives Sub-Group can review for potential consensus at our upcoming call on Monday May 2nd. Thanks, - Judy At 11:55 AM 4/25/2011 -0400, Judy Brewer wrote: >DRAFT for discussion purposes only.... partly for approach, party >for content... > >[DRAFT] > >Dear All, > >With regard to the HTML Working Group Co-Chairs' decisions, as >described in the following email... > >http://lists.w3.org/Archives/Public/public-html/2011Apr/0451.html > > >...which discussed the following information... > >>There is a basic disagreement in the group on the validity >>requirements for alt. The result was two issues, six change >>proposals, and a straw poll for objections: >> >>http://www.w3.org/html/wg/tracker/issues/31 >>http://www.w3.org/html/wg/tracker/issues/80 >>http://lists.w3.org/Archives/Public/public-html/2010Jul/0050.html >>http://www.w3.org/html/wg/wiki/ChangeProposals/ImgElement20090126 >>http://www.w3.org/html/wg/wiki/ChangeProposals/ImgElement20100706 >>http://www.w3.org/html/wg/wiki/ChangeProposals/ImgElement20100707 >>http://www.w3.org/html/wg/wiki/ChangeProposals/ImgElement20100510 >>http://www.w3.org/html/wg/wiki/ChangeProposals/ImgElement20100504 >>http://www.w3.org/2002/09/wbs/40318/issue-31-80-validation-objection-poll/results > > >...and which arrived at the following six conclusions... > >>Therefore, the HTML Working Group hereby decides that: >> >> * The presence of aria-labelledby does not make missing alt conforming. >> * The presence of role=presentation does not make missing alt conforming. >> * The presence of <meta name=generator> makes missing alt conforming. >> * Use of private communications does not, in itself, make >> missing alt conforming. >> * The presence of title makes missing alt conforming. >> * The presence of figcaption makes missing alt conforming. > > >...and which furthermore proposed addressing these through >implementation of a combination of the following two Change Proposals... > >>The two Change Proposals closest to these results are those identified >>as Requirement Set 1 and Requirement Set 4: >> >> http://lists.w3.org/Archives/Public/public-html/2010Jul/0050.html >> http://www.w3.org/html/wg/wiki/ChangeProposals/ImgElement20100707 >> >>These Change Proposals agree with each other and with the WG decision >>on aria-labeldby, role=presentation and figcaption. >> >>On the generator mechanism and the title attribute, Requirement Set 1 >>aligns with the WG decision: >> >> http://lists.w3.org/Archives/Public/public-html/2010Jul/0050.html >> >>On the email exception, Requirement Set 4 aligns with the WG decision: >> >> http://www.w3.org/html/wg/wiki/ChangeProposals/ImgElement20100707 >> >>Thus, overall, the WG adopts the Requirement Set 1 proposal with >>regards to aria-labelledby, role=presentation, <meta name=generator>, >>title and figcaption; but Requirement Set 4 with regards to the email >>exception. > > >...we note that the following information was not considered. The >respondents on the surveys mentioned above had not anticipated that >this information would be unknown to the Co-Chairs, and so have >described this information in some detail within this mail, and >presented test samples to illustrate failures associated with the >proposed approaches. These clarifications follow. > > >On the Co-Chair's decision on aria-labelledby: > >> * The presence of aria-labelledby does not make missing alt conforming. > >The purpose of alt is to provide alternative text on images, and to >allow a user agent to render text in place of the images when images >are turned off. > >As an example, applications such as Yahoo! mail render alt text for >images when web page content is embedded in a mail message. This >allows applications and browsers to only fetch images if a user >really needs them, improving download performance; and providing a >label to explain to the sighted user what is missing. > >aria-labelledby is used to reference a label that is already visible >on the page, similar to an image caption. Authors put these captions >or labels in order to assist the sighted user in providing context >about the user. > >Both the label and the alt text serve the same purpose when images >are turned off; and both provide a label. It does not seem >appropriate to force the author to provide two labels for the same >image, and to have two labels rendered when images are turned of. >Both will supply a label or "name" for the image in the accessibility API. > >Consequently, we request that the Co-Chairs consider allowing >aria-labelledby to be used to point to a label as a suitable >alternative to alt. > > >On the Co-Chair's decision on role=presentation: > > > * The presence of role=presentation does not make missing alt conforming. > >Alt having a value of "" tells the user and assistive technology >that the image is presentational. Yet, with alt="" an assistive >technology (AT) must still filter out the image when it has no >intrinsic value other than to be decorative or be used as a spacer. > >Unlike alt="", role="presentation" has the added value of removing >the image from the accessibility API object tree, effectively >filtering out the image and improving assistive technology >performance. Furthermore, a role of presentation is to state the >intent of the author in a declarative fashion. For these reasons, >role="presentation" should be considered a suitable alternative to >requiring alt when it adds no meaningful information to an AT. > >As background, note that in most cases, browsers map browser content >to platform accessibility APIs, and an accessible object with a >standard API interface is created for each DOM object in a web page. >These objects are referenced and communicated with by an AT to >process accessibility information about visible objects in the web page. > > >On the Co-Chair's decision on the presence of title making missing >alt conforming: > > > * The presence of title makes missing alt conforming. > >Title has a completely different function from alt in HTML. > >Title is used to generate a tooltip, and is invisible when images >are turned off. Alt does not generate a tooltip, and is visible when >images are turned off. > >If title is allowed as alternative text over alt it will break >applications such as Yahoo! mail; it will also break a commonly-used >feature, in less powerful mobile phones, where images are turned off >to improve performance. > >If title were to be used in place of alt then when images are turned >off in the browser, nothing meaningful will be shown in the browser. > >Furthermore, having title take precedence over alt will result in >tooltips being generated on decorative images and spacers, which >would do tremendous harm to the user experience. > >It should be noted that title is used as a last resort when other >measures cannot be employed to compute the label or "name" of an >object in the accessibility API mapping for browsers. > >Please note the following demonstrations of failures resulting from >the proposed approach: > >http://www.paciellogroup.com/blog/misc/HTML5/alt-tests/screenshots.html > > >On the Co-Chair's decision on the presence of figcaption making >missing alt conforming: > >* The presence of figcaption makes missing alt conform > >[clarification pending] > > >Please let us know if additional clarification is needed, and thank >you in advance for your re-consideration. > >Regards, > >....
Received on Monday, 25 April 2011 17:22:15 UTC