HTML 5 Draft Standard - 30 July 2009 - Huihoo

36
Note: There is no implied relationship between document conformance
requirements and implementation conformance requirements. User agents are
not free to handle non-conformant documents as they please; the processing
model described in this specification applies to implementations regardless of
the conformity of the input documents.
User agents fall into several (overlapping) categories with different conformance requirements.
Web browsers and other interactive user agents
Web browsers that support the XHTML syntax (page 901) must process elements and
attributes from the HTML namespace (page 885) found in XML documents as described in
this specification, so that users can interact with them, unless the semantics of those
elements have been overridden by other specifications.
A conforming XHTML processor would, upon finding an XHTML script element in an
XML document, execute the script contained in that element. However, if the element
is found within a transformation expressed in XSLT (assuming the user agent also
supports XSLT), then the processor would instead treat the script element as an
opaque element that forms part of the transform.
Web browsers that support the HTML syntax (page 781) must process documents labeled as
text/html as described in this specification, so that users can interact with them.
User agents that support scripting must also be conforming implementations of the IDL
fragments in this specification, as described in the Web IDL specification. [WEBIDL]
Non-interactive presentation user agents
User agents that process HTML and XHTML documents purely to render non-interactive
versions of them must comply to the same conformance criteria as Web browsers, except
that they are exempt from requirements regarding user interaction.
Note: Typical examples of non-interactive presentation user agents are
printers (static UAs) and overhead displays (dynamic UAs). It is expected
that most static non-interactive presentation user agents will also opt to
lack scripting support (page 36).
A non-interactive but dynamic presentation UA would still execute scripts, allowing
forms to be dynamically submitted, and so forth. However, since the concept of
"focus" is irrelevant when the user cannot interact with the document, the UA would
not need to support any of the focus-related DOM APIs.
User agents with no scripting support
Implementations that do not support scripting (or which have their scripting features
disabled entirely) are exempt from supporting the events and DOM interfaces mentioned in
this specification. For the parts of this specification that are defined in terms of an events
model or in terms of the DOM, such user agents must still act as if events and the DOM
were supported.