KD013 Extensiblity

* KD 013
4.2.3. Extensibility
""" Good practice:  Extensibility mechanisms
  A specification SHOULD provide mechanisms that allow any party to  
create extensions that do not interfere with conformance to the  
original specification."""

This Good Practice is too general. Extensibility MUST NOT be a SHOULD.  
Extensibility is a very delicate topic which has to be considered  
carefully by a group designing a format. It CAN be absolutely wise to  
forbid extension.
Choosing extensibility leads to benefits and drawbacks. See for this  
topic
	http://www.w3.org/TR/qaframe-spec/
	http://www.w3.org/TR/spec-variability/
	
	1. If extensions is considered as beneficial, the specification MUST  
provide a mechanism to do so.
	2. If such a mecanism is given, it MUST not interfere with the  
conformance of the section

I would add a link from this section to the QA Framework Specification  
Guidelines and to the Variability in Specifications document.
	http://www.w3.org/TR/qaframe-spec/
	http://www.w3.org/TR/spec-variability/

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | Our years, our debts, and our enemies
http://nwalsh.com/            | are always more numerous than we
                              | imagine.--Charles Nodier