wiki:interaction-design/conceptual-model

Version 26 (modified by nhoyt, 7 years ago) (diff)

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Conceptual Model

A conceptual model describes all of the objects, actions and concepts, and their relationships within a system.

This conceptual model is for web accessibility evaluation.

A. Web resource-related objects

  1. node: an HTML element node, text node or other component of a web page
  2. page: an HTML document, including its top-level element node

B. Web resource-related actions and results

  1. resource selector: a definition that specifies how to select a set of resources from a web page
  2. target resources: the set of web resources that results from applying a resource selector

C. Evaluation-related objects

  1. accessibility rule: the requirements that one or more target resources must meet
  2. rule category: a grouping of rules with related accessibility requirements or target resources
  3. rule mapping: the membership properties of an accessibility rule within a ruleset
  4. rule set: a collection of rule mappings tailored for a particular audience and based on a set of standard requirements (e.g. WCAG 2.0)

D. Evaluation-related actions and results

  1. rule evaluation: the application of an accessibility rule to its target resources
  2. node result: information derived from a rule evaluation with respect to a single target node
  3. rule result: the result of a rule evaluation with respect to all of its target resources on the page (both individually and collectively)
  4. summary result: an aggregation of node and/or rule results (organized in various ways)
  5. result type: "pass", "manual check", "not applicable", "violation" or "warning"
    • Note: a rule mapping specifies whether a rule is of type "required" or "recommended"
    • result types common to both required and recommended rules: "pass", "manual check", "not applicable"
    • result type when a required rule fails: "violation" (see rule mapping)
    • result type when a recommended rule fails: "warning" (see rule mapping)

Further breakdown of evaluation-related objects

accessibility rule

  • id: unique identifier for the rule (referenced by rule mappings and rule results)
  • scope: "node" or "page"
  • resource selector: the definition for selecting target resources related to this rule
  • resource properties: the specific properties of the target resources that pertain to the rule definition
  • definition: the markup patterns or requirements that must be present in, or met by, the target resources
  • summary: a concise or abbreviated statement of the rule definition
  • purpose: the significance of the rule for users with disabilities
  • techniques: the specific markup patterns that are required or recommended for passing the rule; may be empty if covered by the rule definition
  • corrective action: concise description of what needs to be done to remedy a failure or perform a manual check
  • category: the rule category to which the rule belongs
  • external requirement id: reference to an external requirement (e.g. a Success Criterion in WCAG 2.0) to which the rule is related
  • language dependency: the language upon which the rule depends, or "none" if no dependency
  • informational links: links to examples, articles or other resources relating to the rule definition and/or techniques

rule category

  • a grouping of rules with related accessibility requirements or target HTML objects
  • examples of categories based on rules related by accessibility requirements: Color Contrast, Landmarks, Language
  • examples of categories based on rules related by target HTML objects: Images/Media, Controls, Headings, Links, Lists, Tables, Abbr/Acronym

rule mapping

  • id: identifier of the accessibility rule to which the following properties are being mapped
  • type: "required" or "recommended"
  • enabled: "true" or "false"

ruleset

  • a collection of rule mappings tailored for a particular audience and based on a set of standard requirements (e.g. WCAG 2.0)
  • Note: via rule mappings, the rule type (required or recommended) for any given rule can vary from one ruleset to another
  • Note: via rule mappings, one ruleset may include rules that other rulesets omit and vice versa (using the "enabled" property)

Further breakdown of evaluation-related results

node result

  • node-level information that relates to a rule evaluation
  • node-level result: one of the result types defined above or "none"
    • for rules with "node" scope, the node-level result will be one of the result types defined above
    • for rules with "page" scope, the node-level result may be one of the result types, or possibly "none" indicating that the node simply played a secondary role in determining the page-level result
  • resource properties and their values at the node level as applicable

rule result

  • id: identifier of the accessibility rule that was applied to obtain this result
  • node results: the set of node results used in the overall determination of the page result
  • page-level result: one of the result types defined above

summary result

  • at lowest level, a single rule result
  • aggregation of rule results by HTML-object:
    • element: all results for all rules that apply to element
    • element group: all results for all rules that apply to any or all elements in the element group
    • page: all results for all rules that only apply at page level; all results for all rules that apply to all element groups on the page; all results for all rules that apply to all elements on the page; all of the above
    • site: all page-level aggregations across an entire site
  • aggregation of rule results at page level by WCAG success criteria
  • aggregation of rule results at page level by WCAG Level (A, AA, AAA)
  • aggregation of rule results at page level by rule type (required, recommended)
  • a list of all rules that were not evaluated (enabled = false)

Additional resources