[ACTION-1520][ISSUE-679] Proposed definition of "value"

Definition of "Value"
Value is the literal content of an ARIA defined property, state or role attribute that provides important information communicated to users through accessibility APIs.   All role values are defined from a specific set of role tokens and role values that are not defined in the token list are considered an authoring error. Many states and properties accept a specific set of tokens as values, often with one of the tokens being considered the default value.   Other aria states and properties accept and IDREF or a list of IDREFs to define relationships between elements or define labeling and description information for a section of a page, an element or widget.  Some properties used for labeling and description accept explicit string values.  Note the resulting string values of properties defined for labeling and description should be designed to help users interacting with the page or web application understand the content and features of the web page or application.

Action-1520:
https://www.w3.org/WAI/PF/Group/track/actions/1520

Issue-679:
https://www.w3.org/WAI/PF/Group/track/issues/679