XML Accessibility Guidelines

Charles McCathieNevile - 7 august 2002

Extreme Markup 2002

Slides: http://www.w3.org/2002/Talks/0807-xm-xag

What?

• Another set of WAI guidelines
• How to make XML languages that support accessibility
• Produced by PFWG from experiences in review
• "Mostly Public" development

Related work

• Device Independence principles
• Hollenbeck, Rose, Masinter "how to write XML"
• QA Framework, specification guidelines
• WCAG, ATAG (first public user)
• Multimodal Interaction

Executive summary

1. Ensure that authors can associate multiple media objects as alternatives
2. Create semantically-rich languages
3. Design an accessible user interface
4. Document and export semantics

1 - alternative media objects

• Equivalent to "equivalent alternatives" in *AG
• Explicit association required
• Unconstrained to type

  - allow rich text, video, sign languages, audio, etc.

• Use existing "accessible" techniques (e.g. include SVG)

XAG 1 and Extreme

1.1: Provide a mechanism to explicitly associate alternatives for content or content fragments

Pass? for images ( by allowing graphic in figure).

must include a pointer to the thing illustrated by figure

1.2: Define flexible associations, where a given kind of relationship can link to or from objects of varying types without constraint

Pass? xref anywhere, but what exactly is linked?

1.3: Reuse existing accessibility modules to indicate alternative-equivalent associations

Fail? Known issue: Unclear what. Markup or modelling level

so: Use SVG for images? SMIL test attributes?

XAG 1: other examples

• SMIL test-attributes allow for multiple associations (1.1, 1.2)
• Extreme - use SVG for images instead of postscript? (1.3)
• Metadata potentially provides explicit association (SMIL, SVG, VoiceXML,...)
• VoiceXML uses defined Lexicon, allows graphic presentation

  - e.g. the classic example - Order a Pizza.

• HTML alt attribute is text-only, object element specifies order.

2 - semantically rich languages

• Allow tools to decompose information
• Classify, identify, summarise and structure
• Use existing XML standards
• Seperate style and content, allow for metadata

XAG 2 and Extreme...

2.1 Ensure all semantics are captured in markup in a repurposeable form

Fail? Text works.... but not content in graphic

2.2 Separate presentation properties using stylesheet technology/styling mechanisms

A clear pass. As one would expect here ;-)

2.3 Use the standard XML linking and pointing mechanisms (XLink and XPointer)

Not applicable. (issue: does Hlink pass?)

2.4 Define element types that allow classification and grouping (header, etc)

Pass: front, body, section, with title

XAG 2 ... continued ...

2.5 Provide for a full containment model with chunks of reasonable size

Pass. section, subsec1, and other structure are good.

2.6 Define element types that identify important text content

Pass. abbreviations, references, etc.

(Issues: how do you decide what is important? Image parts?)

2.7: Provide a mechanism for identifying summary / abstract / title

Pass. Beautiful

2.8 Don't overload the semantics of elements

Pass. (is this about style or accessibility?)

XAG 2 ...and continued

2.9 Reuse accessible modules from schema as originally specified / intended

Pass? Nothing "re-used". (See also 1.3)

2.10 Allow association of metadata with distinct elements and groups of elements

Fail? (Issue: you can for metadata that can point...)

2.11 Specific checkpoint for Final-form dialects.

Not Applicable. (Issue: What really is final form?)

XAG 2: other examples

• VoiceXML - alternative for audio (2.1)
• Using CSS or specifying presentation seperation (2.2)
• SVG: g, title (2.5, 2.7)
• HTML - code, sample, var, kbd, q, blockquote (2.6)
• SVG switch, animate (2.9), metadata (2.10), Xlink (2.3)
• XSL-FO - "where did this come from?" (2.11)

3 - design for accessible UI

(or, Remember there are users)

• Provide default styles and navigation for different media
• Allow for device-independent interaction
• Allow for user control or override of timing

XAG 3 and Extreme

3.1 Provide default style sheets for multiple output modalities where possible

Pass: XSLT to HTML gives us various media

3.2 Define navigable structures that allow discrete, sequential, structured, and search navigation functionalities

Pass: Good structure can be used

3.3 Use CSS or XSLT to describe a basic outline view

Fail: But this is 10 minutes CSS or XSLT

3.4 Use a device-independent interaction and events model / module

Not applicable

3.5 Allow for user control of interaction timing - rate of change, external events triggering document changes, etc.

Not applicable

XAG 3: other examples

• CSS 2 style for HTML 4 (3.1)
• Daisy: navigation structure (3.2)
• A header-based outline for XHTML (3.3)
• SVG: onactivate, onfocus (3.4)
• Spec: User Agents can allow timing override (3.5)

4 - document the semantics

• Ensure human- and machine-accessible documentation

  - use schema languages.

• Document *AG techniques (for authors, tools, users)
• Include accessibility conformance requirements

  - for tools, and for validity, as achievable

XAG 4 and Extreme

4.1 Ensure human-readable documentation conforms to WCAG double A

Fail - DTD is too complex for many people. DTD + CSS/XSLT?

4.2 Provide a machine-understandable means/mechanism to get from a document instance to the schema

Pass: Doctype declaration

4.3 Provide explicit human readable definitions for markup semantics

Pass - the DTD does say this

4.4 Use a schema language that can support explicit human-readable documentation or annotation of semantics

Fail. DTD doesn't point to the semantics on a per-element basis

XAG 4 and Extreme - more

4.5 Provide semantic relationships to other schemata where appropriate and possible

Pass with XSLT to HTML

4.9 Do not assume that element or attribute names provide any information about element semantics

Pass. (Issue: relationship with 4.3?)

4.10 Document navigable structures. Describe how discrete, sequential, structured, and search navigation mechanisms should work

"Fail". But this is 5 minutes work.

XAG 4 and Extreme - the rest

Fail all of:

• 4.6 Document accessibility features of the application
• 4.7 Include accessibility requirements in conformance requirements
• 4.8 Document techniques for WCAG, ATAG, and UAAG with respect to the XML application

XAG 4: other examples

• W3C Specs are getting better at WCAG (4.1)
• Language or Schema mapping (4.5)
• SVG or HTML Accessibility work (4.6, 4.7, 4.8)

Known Issues

• Ordering / grouping / redundancy (this is a draft)
• Relationship to "good style", i18n, etc. guidelines
• How to deal with "final form" languages like XSL-FO
• Applicability to languages like SOAP, RDF
• Reliance on tools providing XML accessibility
• Need review, editing, testing, review

Questions?

Feedback welcome anytime: wai-xtech@w3.org

Latest editor draft: http://www.w3.org/WAI/PF/XML