Basic Concepts

Rule: A low-level accessibility conformance requirement with numerous components, the most basic of which are a definition, an evaluation function, and result messages. When a rule is evaluated, it is assigned a rule result value. List of current rules.
Target resources: The set of HTML elements to which a particular rule applies. These include familiar elements such as div, img and input, as well as a pseudo-element designated as page or website, which is a placeholder for the document element or a feature for related web pages. When a rule is evaluated, each of its target resources is assigned a result value.
Evaluation: The application of all evaluation functions of all rules in the selected ruleset to their corresponding target resources in a web page, and the subsequent collection of all evaluation results and messages, at both the rule and element levels, into a dataset.
Rule result: The aggregate result of a rule evaluation with respect to its target resources (all of its target elements and/or the entire page).
Element/Page/Website result: The result of a rule evaluation with respect to one of its target elements.
Rule scope: WCAG requirements not only apply to individual html elements, but also requirements for page and website features. Page and website requirements often require some type of human interpretation to determine if requirements have been meet and designers need to be aware of these requirements when identifying the features of a website or web application.; element: A WCAG requirement for a specific html element or an element with an ARIA role, property or state. For example, an img element must have an accessible name (e.g. alt attribute value).; page: A WCAG requirement that applies to a feature of a web page. For example, a web page must have a main landmark.; website: A WCAG requrement that applied to pages within a website or application. For example, consistent navigational links in each page within website.