- From: Ian B. Jacobs <ij@w3.org>
- Date: Wed, 29 Jan 2003 13:06:15 -0500
- To: w3c-wai-gl@w3.org, ij@w3.org
Dear WCAG WG, After a discussion with Wendy about Lee Roberts' recent email [1] about checkpoint 5.4 (user interfaces), Wendy suggested that I share my thoughts with the WCAG WG. [Thanks again to Wendy for reviewing this email.] This email focuses on questions of conformance, and relies fairly heavily on the conformance mechanisms used by UAAG 1.0 [2]. I'd like to discuss three questions in this email: 1) What user agent features does WCAG 2.0 assume are implemented? 2) How far should WCAG 2.0 go in requiring as part of conformance to WCAG 2.0, that the author be able to show implementation of those features? 3) Is there any reason to distinguish content that creates a custom interface from other content? The WCAG WG faces a number of challenges on the subject of user agent dependencies. First, the WG must identify which user agent features are expected to be implemented in order for the content requirements of WCAG to work. For instance, WCAG requires authors to provide text equivalents under the assumption that the user agent will make them available to the user. Since WCAG is format-neutral, it's difficult to state generically what user agent features must be implemented. It would be easier to be able to say something like "Since we are only talking about SVG, the SVG viewer must be able to do the following..." Second, since WCAG is format-neutral, and the Web is a diverse environment with old and new formats, the WCAG WG faces the challenge of ensuring that for a given piece of content in a format (call it "F"), there really is an accessible user agent out there that implements F. [1] http://lists.w3.org/Archives/Public/w3c-wai-gl/2003JanMar/0114 [2] http://www.w3.org/TR/2002/REC-UAAG10-20021217/conformance ----------------------------------------------------------- 1) What user agent features does WCAG 2.0 assume are implemented? ----------------------------------------------------------- Since UAAG 1.0 is a Recommendation, it should be possible to identify required user agent features using "UAAG 1.0 conformance profiles." We didn't have UAAG 1.0 when writing WCAG 1.0, and so we ended up with the "until user agent" provisions. I hope that WCAG 2.0 will not include any software requirements other than in terms of UAAG 1.0 profiles. This means, for example, that the "level 2 success criteria" of checkpoint 5.4 in the 8 Jan 2003 WCAG 2.0 WG draft should be deleted: <delete> 2. device-independent access to functionality is provided 3. accessibility conventions of the markup or programming language (API's or specific markup) are used </delete> UAAG 1.0 includes both of those requirements, so they can be safely dropped from WCAG 2.0. If UAAG 1.0 does not include something required by WCAG 2.0, that's unfortunate, and the WCAG WG should let the UAWG know. In that case, WCAG 2.0 might need to include a software requirement. I think it's more likely that UAAG 1.0 has more requirements that WCAG 2.0 needs. And therefore, the two WGs should work together to establish a suitable UAAG 1.0 conformance profile that meets the needs of the WCAG WG. That work should start with a statement from the WCAG WG of which user agent features are assumed. Once a profile has been defined, checkpoint 5.4 should be deleted. Then, the WCAG conformance chapter can say: (1) In order to conform to WCAG 2.0 for a format F, content in F must satisfy WCAG 2.0 checkpoints. (2) As part of a conformance claim, the author must also make a UAAG 1.0 conformance claim (which includes a conformance profile). Or, informally, the author has to: - Ensure that the content is accessible, and - Ensure that a proper delivery context exists. WCAG 2.0 checkpoints should only be requirements related to the characteristics of content. Requirements related to other conditions in the world (e.g., the existing of UAAG-conforming user agents) belong elsewhere. Aside from being a simpler model, this separation promotes automatic conformance checking. Assertions by the author belong in conformance claim: - "This is the version of WCAG 2.0 I'm referring to..." - "My content conforms to WCAG 2.0 requirements as follows..." - "I am assuming the following UAAG 1.0 profile. ..." And so on. ----------------------- On conformance profiles ----------------------- WCAG 2.0 is format-neutral, and that makes the construction of a UAAG 1.0 conformance profile difficult. It would be much easier to say, for example, "If you are implementing SVG, then your user agent has to satisfy the following UAAG 1.0 profile." When the format is not known in advance, the profile is harder to build. One way to help is to use the UAAG 1.0 content type labels. Thus, WCAG 2.0 could say "If your format F is a format for creating images, then your user agent must satisfy the following UAAG 1.0 profile for images..." That would help for the handful of content types listed in UAAG 1.0. This suggests to me that WCAG 2.0 conformance profiles might be useful. Conformance profiles allow flexibility in conformance claims but increase complexity. Conformance profiles were perhaps the hardest issue the UAWG faced for UAAG 1.0. I am happy to discuss this further. WCAG 2.0 could allow authors to indicate different conformance profiles. However, for the sake of simplicity, there should be a few simple default profiles for common authoring practice. In WCAG 1.0, there were three options: levels A, double A, triple A. In UAAG 1.0, there are several more. We don't have enough experience with UAAG 1.0 conformance claims yet to know whether we've hit the sweet spot in trying to find a balance between flexibility for claimants and simplicity for those who read claims. ---------------------------------------------------------- 2) How far should WCAG 2.0 go in requiring as part of conformance to WCAG 2.0, that the author be able to show implementation of those features? ---------------------------------------------------------- A conformance claim is a set of assertions. In UAAG 1.0 terms, a claim is "well-formed" if it contains all of the proper information (e.g., a conformance profile). A claim is "valid" if the user agent ACTUALLY satisfies the identified requirements. Today, W3C does not validate claims. This is relevant to the question of whether the author should be required to show that a conforming user agent actually exists (or, for that matter, that the content ACTUALLY satisfies the content requirements of WCAG). WCAG 1.0 did not require the author to show implementation of user agent features as part of conformance to WCAG 1.0. I have the sense that the WCAG WG wants to go further for WCAG 2.0, but that is somewhat problematic since W3C does not act as an assuring party today. There are other challenges to including a requirement to show real implementation, such as How many user agents must be demonstrated? On how many platforms? What if the user agent is not available for free? Some of that work is done in Candidate Recommendation period: the WG advances once it shows sufficient implementation. But, for instance, the evaluation reports of the UAWG include big disclaimers that they are not validity assessments. ---------------------------------------------------------- 3) Is there any reason to distinguish content that creates a custom interface from other content? ---------------------------------------------------------- In my opinion: No. The desired outcome is that the user be able to use all content via an accessible user agent. If the author creates content in a format F, then (based on what we said above), the author had better be sure that there are accessible implementations of F out there, whether F is HTML or something less widely deployed. ------- Summary ------- a) Delete checkpoint 5.4 b) Make it a conformance claim requirement that the author include a UAAG 1.0 conformance claim. c) Challenge: Design WCAG 2.0 conformance profiles. d) Challenge: Identify appropriate UAAG 1.0 conformance profiles. e) Challenge: How to assess the validity of both the WCAG and UAAG conformance claims. -- Ian Jacobs (ij@w3.org) http://www.w3.org/People/Jacobs Tel: +1 718 260-9447
Received on Wednesday, 29 January 2003 13:07:34 UTC