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Glossary

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Alternate: Refers to the mechanism through which equivalents are provided and can be chosen from by the user.

Alternative: This term is to be avoided. (Rationale: when referring to content, being "alternative" suggests that an equivalent is more important than another, yet for a blind user, alt text for example is far more important than the image.)

Compatibility: For HTML5, compatibility, refers to the principles that changes to HTML should be done in a way that is sensitive to the large base of existing content and the base of existing user agents (see this email for further discussion).

Equivalent: Content that conveys the same meaning as other content, through a different means. For instance, both an image and its alt attribute are to convey the same message. Thus "equivalent" refers strictly to content, not to any mechanism.

Inclusive Design: Inclusive design means developing systems, products or web sites flexible enough to serve the broadest possible range of users. It provides access to users with disabilities and provides better usability for everyone.

Fallback: The UA mechanism of automatically presenting one alternate when the 'main' equivalent(s) can for whatever reason not be presented

Namespace: Refers to a mechanism to ensure specific meanings or individual objects are uniquely identified by distinct names. Generally a namespace uses a prefix, or reverse domain notation or IRI to ensure newly created names within the namespace have distinct meanings and do not collide with other newly created names from other namespaces. By separating names into namespaces separate individuals or organization can freely establish new unique names within their domain with confidence those names will not collide with names in other domains. Currently, XHTML 1.0 and 1.1 use a namespace IRI of "http://www.w3.org/1999/xhtml" that traditionally maps to either the default namespace (no prefix) or to a prefix of "html". Within HTML names include: element names, attribute names, DOM APIs names, attribute enumerated values, and named character entities. To preserve the HTML namespace these names must be reserved for their original meanings to avoid name collisions. The introduction of new elements, attributes, enumerated values, APIs or character entities should involve new names. (see this email thread for further discussion)

Racine: The part of a URI before the fragment identifier. In http://example.oom/foo#bar , the racine is http://example.com/foo and the fragment identifier is bar. See Cwm Built-in Functions.

Semantics: Semantics refers to meaning. e.g. elements and attributes in HTML describe the meaning of information/content. Semantic markup for the sake of semantic markup is a good idea. Writing that means nothing (non-semantic writing) is the bad idea: it wastes the readers time. Likewise, markup that means nothing is also a bad idea. That is not to say that marking up text with bold and italics means nothing. Rather its meaning is less precise and require greater heuristics to interpret than markup that includes semantic constructs. RTF and TeX for example have many facilities for marking up meaning in a non-hierarchical fashion using common typographic/visual conventions. That is a very different approach than HTML where the document is usually markedup with precise device independent semantics that are then styled using different device dependent presentation idioms. For more information see Robert Burns post.

Usability: Usability is the art and science of designing systems or products that are effective, efficient, engaging, error tolerant and easy to learn. Usability and accessibility are often confused. For instance some believe that a usable web site is accessible and vice versa. The two are not exclusive, but it is important to understand the difference. Usability means intuitive and easy to use. Accessibility means as barrier-free as possible. Accessibility and usability are closely related, as they both improve satisfaction, effectiveness, and efficiency of the generic user population. But while accessibility is aimed at making systems or products open to a much wider user population, usability is aimed at making the target population happier, more efficient, more effective. Accessibility is actually a prerequisite to usability. If a person can not access a web page he/she certainly can not use it.

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