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Re: The value space of XMLLiteral (was: Re: XML literals poll)

From: Ivan Herman <ivan@w3.org>
Date: Thu, 24 Nov 2011 15:46:29 +0100
Cc: Gavin Carothers <gavin@carothers.name>, RDF Working Group WG <public-rdf-wg@w3.org>
Message-Id: <ED06158B-55A3-43BB-A674-0CC3D17DAB86@w3.org>
To: Richard Cyganiak <richard@cyganiak.de>

On Nov 24, 2011, at 15:25 , Richard Cyganiak wrote:

> On 24 Nov 2011, at 08:54, Ivan Herman wrote:
>> Actually... my claim is that if we use the xml infoset value approach, we can keep silent on canonicalization altogether in our specs, and scrap all references to it. How two valid XML fragments could/should be compared for equality in terms of infosets is not something this WG has to solve; it is an implementation issue that has to be based on what the XML community defines. Not our job.
> 
> An XSD datatype MUST define the identity and equality relations over its value space.
> http://www.w3.org/TR/xmlschema11-2/#value-space
> 
> Saying “the values are XML infosets; you figure out yourself how to compare them” doesn't seem sufficient.
> 

Why? I mean, we do not have to go into some sort of a great detail here. The infoset standard says that 

[[[
An XML document has an information set if it is well-formed and satisfies the namespace constraints described [BELOW]
...
An XML document's information set consists of a number of information items...
]]]

And what we say is that, as far as we are concerned, two values are identical if their information set are identical. I just do not see why we would have to go beyond that.


> The spec also says that you “SHOULD specify a canonical mapping for the datatype if practicable”, which means even if the value space is infosets, the spec SHOULD still say, “the canonical mapping is XC14N”.

Well, it is a SHOULD. In this case, there may not be one such approach. Users MAY use canonicalization; MAY convert their XML into a DOM 2 representation and compare the nodes programatically; etc. Again, I am not sure we have to go into too much details

Ivan



> 
> Best,
> Richard


----
Ivan Herman, W3C Semantic Web Activity Lead
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Received on Thursday, 24 November 2011 14:43:38 GMT

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