Analysis of Applicability in UAAG 1.0

This document:
Last modified: $Date: 2000/11/08 07:48:50 $
This document refers to checkpoints in:
Ian Jacobs, W3C


This document analyzes the concept of "applicability" in the User Agent Accessibility Guidelines 1.0 to determine whether it is necessary to include such a concept in the document.

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Table of contents

1. Background

The UAAG 1.0 has included the notion of applicability since the 9 March 1999 Working Draft (through the 18 August draft). Recently, some members of the Working Group have asked the WG to review the concept:

Refer also to previous discussions of applicability:

Refer also to determining conformance to the UA Guidelines, which tracked how the WG folded minimal requirements into the checkpoints themselves.

2. Summary of applicability provisions

In the 18 August Guidelines, the applicability clause includes the following provisions for when applicability may be "invoked":

  1. Device: Unsupported device
  2. Content Role: Content role (e.g., alternative) cannot be recognized.
  3. Content Type: Content type not recognized by UA.
  4. Uncontrollable properties of a piece of content.
  5. Unsupported technologies. Note: This is kind of unclear, but the suggestion is that it refers to unsupported specifications.
  6. Communication impossible: For example, no way for an AT to communicate with a UA on a particular system (e.g., kiosk).

3. Conclusions

  1. Section 4 lists the checkpoints that seem always to apply because they are not subject to any of the six provisions. While many of the checkpoints seem to not be subject to applicability issues, enough of them are to suggest that the concept should remain in the document in some form.
  2. Section 5 groups the remaining checkpoints by the six provisions above.
  3. The checkpoints about communication should always apply since UAAG 1.0 is designed to create accessible user agents that communicate with assistive technologies. If no communication with assistive technologies is possible, then our expectations will not be met and there should not be conformance.x
  4. Checkpoint 5.7 is the only checkpoint that is currently covered by the "unsupported technologies" provision. It can be fixed.
  5. This leaves four applicability provisions that seem to be significant:
    1. Unsupported content type
    2. Unsupported content role
    3. Unsupported rendering type
    4. Urecognized or uncontrollable properties
  6. For these four provisions, I propose the following statements in the document:
    1. This document does not require support for a particular content type. If a user agent does not render a content type at all (e.g., for audio, video, scripts), it is not required to satisfy checkpoints with requirements for that content type.
    2. Some checkpoints refer to the role or purpose of content (e.g., tables, text equivalents, captions, etc.). If a user agent cannot recognize through markup the role or purpose of an element, it is not required to satisfy checkpoints involving that role, for that element.
    3. This document does not require support for a particular rendering. User agents are not required to satisfy checkpoints that refer to renderings that the UA does not support in its native user interface. For example, user agents are not required to support speech, but if they do, speech requirements apply.
    4. Some checkpoints refer to properties of content (e.g., video speed, audio volume, etc.). If a user agent cannot recognize or control the properties of an element, it is not required to satisfy checkpoints involving those properties, for that element.

4. Checkpoints where applicability is not important

The following checkpoints always apply:

5. Checkpoints where applicability is important

5.1 Unsupported device

For example, an audio user agent may not have to allow control of text size. I think these checkpoints are more about rendering than device.

5.2 Unrecognized content role

Other checkpoints:

5.3 Unrecognized content type

Here "content type" means MIME type.

5.4 Unrecognized or uncontrollable properties

5.5 Unsupported technologies

I propose to integrate applicability in this checkpoint since it only applies when the UA supports CSS.

5.6 Communication impossible

I propose that the following checkpoints always apply since the scope of this document has been narrowed to address general purpose user agents meant to interact with assistive technologies. Therefore, communication with them is a prerequisite.