Notes on discretionary behavior in User Agent Accessibility Guidelines 1.0

This version:: http://www.w3.org/WAI/UA/2001/10/ts
Last modified::: $Date: 2001/11/01 12:42:05 $
Author:: Ian Jacobs, W3C

Abstract

This document is a prose description of the "discretionary items" of User Agent Accessibility Guidelines (UAAG) 1.0 [UAAG10]. The term "discretionary item" is used here primarily in the sense used in the XSLT test suite [XSLTTEST]: an area of the specification where a conforming user agent may choose one of N options to satisfy a requirement. However, this document explores some additional types of discretionary behavior (e.g., permitted exceptions) that may not (yet, or at least to the understanding of the author) fit into the XSLT framework.

One usage of this document is to indicate which checkpoints may be eliminated from a conformance claim based on different characteristics of the user agent. This should help developers understand that they may have to implement less to conform than they might initially think.

Status of this document

This document has been produced as part of work on test suites being done by the User Agent Accessibility Guidelines (UAWG) Working Group. These are initial notes by the author; this document does not represent Working Group consensus.

I expect to translate the prose descriptions of this document into a machine-readable formalism that will be part of a test suite for UAAG 1.0.

This document is part of a series of accessibility documents published by the Web Accessibility Initiative (WAI) of the World Wide Web Consortium (W3C). WAI Accessibility Guidelines are produced as part of the WAI Technical Activity. The goals of the User Agent Accessibility Guidelines Working Group are described in the charter.

Discretionary items

Note: In addition to the following discretionary items, someone wishing to claim conformance may choose a priority level, which also limits the number of checkpoints that must be satisfied.

Element types

Does the format include links?

If not, eliminate part of checkpoint 10.4 and part of checkpoint 11.5
If so, implement fee links?
- If not, eliminate checkpoint 5.6 and fee link part of 10.3, 10.4

Does the format include tables?

If not, eliminate checkpoint 10.1

Does the format include forms?

If not, eliminate checkpoint 5.5

Does the format include accessibility captions?

If not, eliminate checkpoints 2.5 and 4.6

Does the format include text transcripts?

If not, eliminate checkpoint 2.5

Does the format include auditory descriptions?

If not, eliminate checkpoint 2.5 and

Content type labels

Does the format support text in color?: If not, eliminate checkpoint 4.3
Does the format support background images?: If not, eliminate checkpoint 3.1
Does the format support images?: If not, eliminate image part of checkpoints 3.1 and 3.7
Does the format support animation?: If not, eliminate animation part of checkpoints 3.2, 4.4, 4.5, 4.7, and 4.8
Does the format support video?: If not, eliminate video part of checkpoints 2.5, 2.6, and 3.2
Does the format support audio?: If not, eliminate audio part of checkpoints 2.5, 2.6, 3.2, 4.4, 4.5, 4.7, 4.8, 4.9, 4.10, and 4.11
Is synthesized speech rendering supported?: If not, eliminate checkpoints 4.12, 4.13, 4.14, 4.15, and 4.16

Formats

Is the format a text format?

If not, eliminate checkpoint 2.2

Is the format an HTML or an XML application?

If so, eliminate checkpoint 6.3
If not, eliminate checkpoints 6.1 and 6.2

Do you support CSS style sheets?: If not, eliminate checkpoints 4.17 and 6.8
Do you support a scripting language?: If not, eliminate checkpoints 1.2, 3.4, 9.5, and 9.6
Note: This assumes event handlers are scripts (and not, e.g,. behavior sheets).
Does the format have time-based features?: If not, eliminate checkpoints 2.4, 2.6, and 3.5
Does the format have event handlers or other author-specified input device bindings?: If not, eliminate checkpoints 1.2, 9.5, 9.6, and 11.2
Does the format support client-driven redirects?: If not, eliminate checkpoint 3.6

User interface features

Does the user agent have a graphical user interface?: If not, eliminate checkpoints 3.3, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 5.2, 10.2 (provision 4), 10.4 (provisions 3 and 4), 10.7 (provision 4), and 11.7.
Does the user agent implement a selection mechanism?: If not, eliminate checkpoints 6.5, 7.1, 9.4, 10.2, 10.3, and 5.4
Does the user agent imlement a viewport history mechanism?: If not, eliminate checkpoint 9.4 and part of checkpoint 11.5
Does the user agent implement placeholders (checkpoint 2.3.1b)?: if not, eliminate checkpoint 2.10

Checkpoints with discretionary requirements

2.3 Render conditional content

See four rendering options
Also, per-element view or global

4.1 Configure text size

Range available from conventional utility, or
Range of supported APIs

4.2 Configure font family

Range available from conventional utility, or
Range of supported APIs

4.3 Configure text colors

Range available from conventional utility, or
Range of supported APIs

4.6 Position captions

Either support through markup language, or
Provide overlapping/non-overlapping control

6.3 Programmatic access to non-HTML/XML content

See API cascade

6.4 Programmatic operation

See API cascade

6.5 Programmatic alert of changes

See API cascade

6.6 Conventional keyboard APIs

See API cascade

8.2 Conform to specifications

Either W3C Recommendation, or
Specification that allows conformance to WCAG 1.0

9.3 Move content focus

User agent may include disabled elements in navigation

10.2 Highlight selection and content focus

Range available from conventional utility, or
Range of supported APIs

10.8 Indicate rendering progress

Rendering progress may be implemented in various ways
Proportion may be indicated in various ways

11.1 Current user bindings

Centralized view, or
Distributed view

12.2 Document accessibility features

Either centralized view, or
Integrated view

Permitted exceptions

The following checkpoints include provisions that essentially say "you don't have to do this, and you can still conform":

2.1 (provision 2) and 8.2 (provision 2): May ignore provisions of other spec to conform to UAAG 1.0
2.4 (provision 4) and 4.5 (provision 5): May discard packets
2.9 (provision 1): Not required to render all content in single viewport
2.11 (provision 3): Multi-language configuration not required
3.1 (provision 3): Only two layers of background images
3.1 (provision 2), 3.2 (provision 3), 10.6 (provision 2): Not required to retrieve from Web
3.4 (provision 3): Not required to alert on per-script basis
3.5 (provision 4): Client-side refreshes only.
3.6 (provision 3): Only applies for non-instantaneous redirects
4.2 (provision 3): Substitute font family acceptable to ensure proper rendering
4.4 (provision 5), 4.5 (provision 4), and 4.10 (provision 2): Style effects not required.
4.3 (provision 3): Playback not required when navigating.
4.6 (provisions 3 and 4): Reflow not required, transparency not required
5.3 (provision 4): Some types of viewports may be excluded.
10.3 (provision 2), 10.7 (provision 3): Not for inherited styles.
11.3 (provisions 2 and 3): Not required to override system conventions, not required to cross modalities
11.4 (provisions 4, 5, 6): Single-key mode permitted, not required to override conventions, not for input

Checkpoints that include sufficient but not necessary techniques

The following checkpoints indicate techniques that are sufficient, but not required, for conformance:

2.4 (provisions 2 and 3): time-independent interaction by pausing or equivalent interaction opportunities
2.7 (provision 2): Repair text composition
3.2 (provision 2): Silent/invisible rendering
11.2 (provision 2): Different view per modality

Recommended behavior

The following checkpoints recommend configurability but do not require it: 3.3, 5.1 (provision 2), 5.3 (provision 5), 5.5 (provision 2), 5.6 (provision 2), and 9.3 (provision 2).

The following checkpoint refers to techniques that are satisfactory but not recommended: 3.2 (provision 2), 3.7 (provision 2).

References

[UAAG10]: User Agent Accessibility Guidelines 1.0, I. Jacobs, J. Gunderson, E. Hansen, eds. The latest draft of the guidelines is available at http://www.w3.org/TR/UAAG10/.
[XSLTTEST]: OASIS XSLT/XPath Conformance TC.
[SVGTEST]: The SVG 1.0 Test Suite. Information about the SVG Test Suite is available at http://www.w3.org/Graphics/SVG/Test/. Refer in particular to the test suite manual.

Acknowledgments

I would like to thank Lofton Henderson for discussing discretionary issues with me, and for introducing me to the XSLT test suite framework.