[SpecGL Draft] D4 Define how to handle each deprecated feature

Lynne, Yours to review ;)

D.4 Deprecation

Previous:
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Good Practice:
	Specify the degree of support required for each deprecated feature and  
its conformance consequence. Consider the effect of deprecation on all  
classes of products that implement the specification (e.g., authoring  
tools, user agents).
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Proposal:
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Good Practice:
	Define how to handle each deprecated feature


Meaning:
	A feature is usually defined when there is a better mechanism inside  
the technology, or another technology that could be used, to achieve  
the same effect (with often more possibilities). It is important to  
define the behavior of the different kind of products when they have to  
read or produce deprecated features. The feature is likely to become  
obsolete in the next version of the technology.

Care:
	It will help to establish transition/evolution strategies for the  
users of the technology. It will help a consistent behavior when the  
technology is implemented in different products and will be  
particularly helpful when products can deal with different versions of  
the technology. For example, should a tool, able to read an old version  
of the document, propose helping mechanism or conversion to the new  
method which are preferred.

Related:
	D3. Define error handling for unknown extensions
	
Technique:
	1. Consider the effect of deprecation on all classes of products that  
implement the specification (e.g., authoring tools, converter, user  
agents).
	2. Specify the degree of support required for each deprecated feature
	3. Define its conformance consequence.


Examples:
	"HTML 4.01" [0]
		In the conformance section of HTML 4.01, there is the definition of  
deprecation and what user agents should do. Though the behavior for  
other kind of products is not defined.
		quote [1]: "User agents should continue to support deprecated  
elements for reasons of backward compatibility."


	[0]http://www.w3.org/TR/1999/REC-html401-19991224/
	[1]http://www.w3.org/TR/1999/REC-html401-19991224/ 
conform.html#deprecated	
	MathML 2.0 describes deprecated MathML 1.x features in terms of  
MathML-output-conformant authoring tools, MathML-input-confomrant  
rendering/reading tools, and MathML-roundtrip-conrormant processors.


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