Re: [SpecGL] Proposal for Error mechanisms section

Le jeudi 03 février 2005 à 15:12 -0500, Karl Dubost a écrit :
> Techniques 4.5 GP A
> [[[
> one should keep in mind that extensibility may need new syntax tokens 
> ([WEB-ARCH], extensibility), which can be smoothen by the use of 
> mustIgnore and mustUnderstand policies: in the first case, a processor 
> is required to ignore only the content that it cannot understand, in 
> the second one, it is required to consider as an error that kind of 
> content
> ]]] - http://www.w3.org/TR/2004/WD-qaframe-spec-20041122/
> 
> New text:
> 
> Techniques 4.5 GP A
> 
> one should keep in mind that extensibility may need new syntax tokens 
> ([WEB-ARCH], extensibility), which can be smoothen by the use of two 
> policies:
> 	 * "must Understand": This mechanism is required when the data are 
> critical for the technology, or when their lost would result in major 
> flaws.
> 	 * "must Ignore": This mechanism will be used when the processing of 
> data would create a major flaw in the application. Then it becomes safe 
> to ignore them altogether.

The new text suggests when to use what policy, but doesn't explain what
the policies are - which the old text did, BTW. (as an aside comment,
let's not use the word "required" in an informative part of the
document, this could lead to confusion, esp. since I don't think
anything is required here at all).

Here comes my proposal:
"""
one should keep in mind that extensibility may need new syntax tokens 
([WEB-ARCH], extensibility), which can be smoothen by the use of various
policies:
* a so-called "mustUnderstand" policy, as implemented in SOAP 1.2 by the
mustUnderstand attribute; in this type of mechanism, a processor
encountering a syntax token not defined in the specification is required
to know how to process the said token or must fail for the whole unit
where the token appears 
* a so called "mustIgnore" policy (as implemented in SOAP 1.2 by the
mustIgnore attribute), where a processor not knowing how to process an
unknown syntax token must skip part or the totality of the unit where
the token appears

Which policy to choose depends heavily on the criticality of the
processing of the data, the user experience of applications based on the
said format, etc.
"""

> 
> 
-- 
Dominique Hazaël-Massieux - http://www.w3.org/People/Dom/
W3C/ERCIM
mailto:dom@w3.org