Roles defined by this specification are designed to support the roles used by platform accessibility APIs. Declaration of these roles on elements within dynamic web content is intended to support interoperability between the web content and assistive technologies that utilize
accessibility APIs.
The schema to support this standard has been designed to be extensible so that custom roles can be created by extending base roles. This allows user agents to support at least the base
role, and user agents that support the custom role can provide enhanced access. Note that much of this could be formalized in [XMLSCHEMA11-2]. However, being able to define similarities
between roles, such as baseConcepts and more descriptive definitions, would not be available in XSD.
The domain of web accessibility defines how to make web content usable by persons with disabilities. Persons with certain types of disabilities use assistive technologies (AT) to interact with content. Assistive technologies can transform the presentation of content into a format more suitable to the user, and can allow the user to interact in different ways.
For example, the user might need to, or choose to, interact with a slider widget via arrow keys, instead of dragging and dropping with a mouse. In order to accomplish this effectively, the
software needs to understand the semantics of the content. Semantics is the science of meaning; in this case, used to assign roles, states, and properties that apply to user interface
and content elements as a human would understand. For instance, if a paragraph is semantically identified as such, assistive technologies can interact with it as a unit separable from the
rest of the content, knowing the exact boundaries of that paragraph. An adjustable range slider or collapsible list (a.k.a. a tree widget) are more complex examples, in which various
parts of the widget have semantics that need to be properly identified for assistive technologies to support effective interaction.
New technologies often overlook semantics required for accessibility, and new authoring practices often misuse the intended semantics of those technologies. Elements that have one
defined meaning in the language are used with a different meaning intended to be understood by the user.
For example, web application developers create collapsible tree widgets in HTML using CSS and JavaScript even though HTML has no semantic tree element. To a non-disabled user,
it might look and act like a collapsible tree widget, but without appropriate semantics, the tree widget might not be perceivable to, or operable by, a person with a disability
because assistive technologies might not recognize the role. Similarly, web application developers create interactive button widgets in SVG using JavaScript even though SVG has no semantic
button element. To a non-disabled user, it might look and act like a button widget, but without appropriate semantics, the button widget might not be perceivable to, or
operable by, a person with a disability because assistive technologies might not recognize the role.
The incorporation of WAI-ARIA is a way for an author to provide proper semantics for custom widgets to make these widgets
accessible, usable, and interoperable with assistive technologies. This specification identifies the types of widgets and structures that are commonly recognized by accessibility products,
by providing an ontology of corresponding roles that can be attached to content. This allows elements with a given role to be understood as a particular widget or structural
type regardless of any semantics inherited from the implementing host language. Roles are a common property of platform
accessibility APIs which assistive technologies use to provide the user with effective presentation and interaction.
The Roles Model includes interaction