Determining Applicability of Success Criteria

Colleagues,
One reason that details of the conformance claim are important is that it provisions of the claim relate directly to the determination about which success criteria are applicable. The material below related to that determination.
Ideally, I think that material such that which is below would be included in the UAAG 2.0 document itself. However, that may not be possible so I think that this might be included in a "Note" that is referred to by UAAG 2.0.
Determining Applicability of Success Criteria

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.
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 to 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.
        Based on these assumptions, there are several major rationales for a success criterion not being applicable to a user agent.
a.      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.
b.      The 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.[Is there are better example of this? Or maybe a subtler one involving configuration?]
c.      The required Web content technology is not part of the claim. The web content technology required for a success criterion is not among the named web content technologies. 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.
d.      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, though I am not sure at this moment.]
e.      An alternative means results in equivalent facilitation. An alternative design or technology results in substantially equivalent or greater access the benefits of the user agent than does following the success criterion.

As noted in the UAAG 2.0 document, where a success criterion is declared as not applicable, a rationale must be provided.[Guidance on writing rationales may deserve additional elaboration].


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)