UAAG 2.0 conformance: Determining Which Success Criteria Must Be Met

Colleagues,
This material is an updated version of the document sent last week. Ideally, I think that material such that which is below should be included in the UAAG 2.0 document itself. However, that may not be possible. An alternative approach would be to include this material in a W3C Note that is referred to by UAAG 2.0. Comments are in square brackets (starting with the word "Comment").

Determining Which Success Criteria Must Be Met

Conformance to UAAG 2.0 refers to a user agent's satisfaction of all applicable success criteria. But how does one determine which success criteria are applicable (i.e., must be met or satisfied) by a given user agent? An answer to this question relies on several principles or assumptions of the UAAG 2.0 approach to conformance.
Principles underlying the UAAG 2.0 approach to conformance. Following are several key principles:
1. A user agent may conform at any of several levels. A user agent may conform at any of three levels - level A, AA, and AAA - with the more A's being indicative of a higher degree of accessibility. For example, a user agent seeking conformance at level AA must address not only the success criteria labeled level AA but also those labeled level A. Similarly, a user agent seeking level AAA conformance must address not only the success criteria labeled level AAA but also those labeled levels AA and A.
2. A user agent relies on platform hardware and usually on platform software. Recall that a user agent is any software that retrieves, renders and facilitates end user interaction with Web content. In order for a user agent, which is software, to render content to the senses of the user, it must rely on hardware (e.g., Android device, audio output) to actually produce the stimuli that can be perceived by the senses of the user (see UAAG 2.0 glossary definition of "rendered content"). In addition to mandatory reliance on platform hardware, a user agent typically relies on platform software, such as an operating system, to manage the hardware resources and to provide other services. Therefore, in the UAAG 2.0 approach to conformance, a user agent must rely on a platform consisting of platform hardware and, optionally, platform software to meet the conformance requirements.

        3. Developers of user agents are generally expected to have less control over the capabilities of the platform than they do over the capabilities of the user agent. Therefore, claimants have less responsibility for addressing accessibility limitations imposed by the platform than they do for those of the user agent itself.
        Major rationales. Based on these assumptions, there are several major rationales for a success criterion not being applicable to a user agent.

1. Success criterion level exceeds the claimed level. The success criterion pertains to higher level. The success criterion pertains to a higher level of conformance than the level that is claimed (e.g., the success criterion pertains to level AA where only conformance to level A is claimed). Any success criterion that is of a higher level than the one claimed may be declared as not applicable.
2. Platform does not support the required capability. The capability required by the success criterion is not supported by platform. For example, if the platform hardware supports only monochrome rendering of content, then success criteria related to color modification may be declared as not applicable.[Comment: Is there are better example of this? Or maybe a subtler one involving configuration?] Where this rationale is invoked, the description of the rationale must identify the specify capability or capabilities that the platform does not support.
3. Web content technology is not relied upon. The web content technology required for a success criterion is not among the web content technologies named in the claim as being relied upon to meet the conformance requirements. For example, if the success criterion requires rendering of audio files yet no audio file formats are named, then the success criterion may be declared as not applicable. Where this rationale is invoked, the description of the rationale must identify the relevant web content technologies.
4. Would result in a fundamental alteration. Satisfying the success criterion would result in a fundamental alteration to the nature of the user agent. For example, if the user agent has a specialized purpose to assess visual perception of content, then to render content in audio may invalidate the assessment results, thereby resulting in a fundamental alteration to the nature of the specialized user agent. [Comment: I think that the IMS Global Learning Consortium's APIP (Accessible Portable Item Protocol) standard may also fall under this category.] Where this rationale is invoked, the description of the rationale must describe one or more specific aspects of the user agent's nature that would be violated by following the success criterion.
5. Alternative means are provided. An alternative design or technology results in substantially equivalent or greater access to the benefits of the user agent than does satisfying the success criterion and that alternative is provided. Where this rationale is invoked, the description of the rational must identify the provided alternative and specify how it provides equivalent or greater access that would satisfaction of the success criterion.

Eric G. Hansen
Research Scientist
Center for Validity Research, MS 10R
Educational Testing Service
Princeton, NJ 08541
609-734-5615
For more resources see:
ETS Accessibility Research <http://www.ets.org/research/topics/assessing_people_with_disabilities>
Accessibility Information & Resources<https://sharepoint.etslan.org/rd/ctrvalres/AIR/default.aspx> (ETS internal only)