Accessibility DOM Elements Cache

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Accessibility Home | Issue Tracker | WCAG 2.0 Rules | Evaluation API 2.0 | Ruleset, Rule and NLS Format 2.0 | Cache Objects | Reporting Practices

Cache Overview

The cache is designed to provide information in a object form for use by the OAA rules and rules processing engines. The cache will reduce the need to use DOM requests to collect information needed for the evaluation of a rule.

List Cache Base Object

Computed Style Object

The computed style object contains information about the run time styling of the node, especially the calculation of color contrast and node position.

DOM Object

This serves as the base element object for other element caches

Link Elements Cache

An array of objects with information about A and AREA elements. The link object inherits from DOM Element Base Cache.

 OpenAjax.a11y.cache.links = [{link object 1}, {link object 2},....]

Link Element Object

The link object inherits from DOM Element Base Object.

Headings Cache

An array of objects in document order with information about headings (h1-h6). The link object inherits from DOM Element Base Cache.

 OpenAjax.a11y.cache.headings = [{heading object}, {heading object},....]

Heading Element Object

Images Cache

An array of objects with information about images. The link object inherits from DOM Element Base Cache.

 OpenAjax.a11y.cache.images = [{image object 1}, {image object 2},....]

Image Element Object

Landmark Cache

An array of objects in document order with information about landmarks. The link object inherits from DOM Element Base Cache.

 OpenAjax.a11y.cache.landmarks = [{landmark object 1}, {landmark object 2},....]

Landmark Element Cache

Form Control Cache (under development)

An array of objects with information about form controls.

 OpenAjax.a11y.cache.html_controls = [{control object 1}, {control object 2},....]

Form Control Object

Color Cache (under development)

An array of objects in document order with information about tables.

 OpenAjax.a11y.cache.colorcontrast = [{color object 1}, {color object 2},....]

Color Object

Table Cache (under development)

An array of objects in document order with information about tables.

 OpenAjax.a11y.cache.tables = [{table object 1}, {table object 1},....]

Table Object

Rule and Cache Processing APIs

Consumers of the Rules

Browser Toolbar Developers (Inspection)

• Visualizations of accessibility information
• Information is transient
• Teaching or learning about how rules apply to developers design patterns

Web App Developers (Auditing)

• Reporting
• Archiving
• Correlating (Analysis) multiple results

OAA API Must Support the Following Use Cases

Configure ruleset for evaluation

1. Select a ruleset
2. Specify language
3. Select rule filters (if any)
4. Run selected rules of a ruleset on a document
5. Select evaluation result filters by:
   • Severity (e.g. violations, manual check)
   • Result type

Generate an accessibility report for a document

1. Provide progress information on rules processing
2. Provide evaluation results (in XML, JSON and/or HTML formats)
   • For each requirement list the rules
     • For each rule in the requirement list the nodes that:
       1. Failed
       2. Passed
       3. Require manual checks
       4. Provide a means to identify each node in the list

Inspect a node of the document for accessibility issues

1. For each node provide the following information:
2. List of rules that fail
   • Provide information on why the node failed
3. List of rules that pass
4. List of rules that require manual evaluation
   • Provide data useful for performing manual evaluation for each rule (e.g. from DOM or other Element cache information)
5. List of rules that met a node context, but did not meet test conditions
   • Provide information on what test conditions were not met

Inspect a class or group of nodes for accessibility issues

1. Provide information to identify the nodes in the class or group of nodes
2. For each member in the class or group of nodes, provide a list of:
   1. Rules that fail
      • Provide information on why each node failed
   2. Rules that pass
   3. Rules that require manual checks
      • Provide data useful for performing manual evaluations for the class or group of nodes (e.g. from DOM or other Element cache information)
   4. Rules that met the rule context, but did not meet test conditions
      • Provide information on why the test conditions were not met

Browser Tool APIs

1. Manage Rulesets
   • Enumerate rulesets that are available
   • Validate ruleset and rules with respect to format
   • Add ruleset
   • Add rules to a ruleset(s)
   • Remove rules from a ruleset(s)
2. Select Ruleset
   • for ruleset(id), disable rules ([rule_id1, rule_id2, ...])
   • for ruleset(id), add rule (requirementNumber, rule_object)
   • for ruleset(id), replace rule (rule_id, rule_object)
   • for ruleset(id), define minimum requirement level (requirementLevel)
3. Traverse DOM to create data cache
   • Create data objects in cache (data and cache level test results)
4. Evaluate and Process Ruleset
   • Use cache to provide data for rules
   • Provide information on ruleset evaluation progress (through call back function)
   • for each requirement in a ruleset:
     • for each rule in the requirement:
       • evaluate each node that is in the context of the rule and return a rule result object
   • for each rule result object add to rule results object
     • for each rule results object add to requirement results object
       • for each requirements results object add to ruleset results object
   • for each node in the DOM save rule results associated with that node
5. Use of Evaluation Results
   • For a node in the DOM return evaluation results
     • Rules that passed
     • Rules that failed
     • Rules that require a manual check
     • Rules for which test conditions were not met
     • Information about the node or its context in the document important for evaluating manual checks
   • Use results to generate reports
     • Generate JSON and XML formatted evaluation result data
     • Generate an HTML report of evaluation results
6. Triggers for updating evaluation
   • Change in ruleset or rules
   • DOM node not found in evaluation results
   • Time (after a certain amount of time update evaluation, user preference)
   • User Initiated Events
     • Keyboard events
     • Mouse events
   • Application Initiated changes in content
     • Time (after a certain amount of time update evaluation)
     • Changes in page or node content (DOM Mutation Events on specific nodes)

Cache and Evaluation Refresh Triggers

Potential sources of updates:

• On focus changes
• DOM node not found in cache
• Timeout
• Live regions