[SpecGL Draft] D.3 Prevent extensions from breaking conformance

D.3 Principle: Prevent extensions from breaking conformance

We have forgotten it. I Put it as an issue for now. The text is:


Principle:
  Prevent extensions from breaking conformance

ISSUE: Topic still in discussion by the WG

Extensions must not contradict or negate conformance to the 
specification. If it conformed without the extension, conformance 
should hold true with the extension.

Technique

Include statements in the specification such as:
	• 	Each implementation must fully support all required functionality 
of the specification exactly as specified.
	• 	The use of extensions must not contradict nor cause the 
non-conformance of functionality defined in the specification.
	• 	Extensions must follow the principles and guidelines of the  
specification they extend; that is, the specifications must be extended 
  in a standard manner.

Examples

In XSLT 1.0 [XSLT10], extension attributes (from other namespaces) can 
be present on the official XSLT elements, but they are prohibited from 
changing the specified behavior within the detectability of conforming 
behavior. Thus, an extension attribute can cause the element to perform 
faster but cannot change the result.

-- 
Karl Dubost - http://www.w3.org/People/karl/
W3C Conformance Manager
*** Be Strict To Be Cool ***