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Re: Use of XSD namespace in RDF recommendations

From: Richard Cyganiak <richard@cyganiak.de>
Date: Tue, 4 Sep 2012 12:52:59 +0100
Cc: public-rdf-comments@w3.org
Message-Id: <A3D785DA-E56E-486D-B8EB-66167D22ED1D@cyganiak.de>
To: Richard Smith <richard@ex-parrot.com>
Hi Richard,

On 31 Aug 2012, at 15:12, Richard Smith wrote:
> In WD-rdf11-concepts-20120605 (and other RDF drafts and recommendations), the xsd prefix is typically bound to the following URI:
> 
>  http://www.w3.org/2001/XMLSchema#
> 
> In the XML Schema recommendations (both 1.0 and 1.1), they bind the xs prefix to
> 
>  http://www.w3.org/2001/XMLSchema
> 
> Note the lack of the trailing '#'.  Per the XML namespace recommendation, xsd:string and xs:string are distinct QNames as they have different namespace URIs.
> 
> Most of the time this isn't a problem.  If you're writing RDF, you add the '#'; if you're writing XML Schema, you don't.  But there are situations where the difference does cause surprising consequences.  For example, here is a cut down version of a real case I recently had to investigate.
> 
>  <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
>      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>      xmlns:dct="http://purl.org/dc/terms/">
>    <xsd:annotation><xsd:appinfo>
>      <rdf:RDF><rdf:Resource about="">
>        <dct:issued
>          rdf:datatype="xsd:gYearMonth">2012-08</dct:issued>
>      </rdf:Resource></rdf:RDF>
>    </xsd:appinfo></xsd:annotation>
>  </xsd:schema>
> 
> I certainly don't think a substantive change is required. But at the risk of advancing the argument that I wrote bad RDF and therefore it's a bug in someone else's standard, I do think a non-normative note mentioning this difference might be in order.

The xs: prefix is conventionally associated with one namespace URI, and the xsd: prefix is conventionally associated with another URI. The URIs are similar -- they differ only in one character.

If a user just uses the URIs as given in the specs, they will be fine. A confusion will only arise if a user is very clever and notices the similarity and tries to "optimize" the namespace declaration; but at the same time is not clever enough to notice the one-character difference. As far as I know, we have no evidence, and no reason to believe, that this is a common confusion.

I don't think that the document is improved by explicitly addressing particular user confusions, *unless* we have evidence that it's a commonly held confusion.

So my vote is for no change.

(It also seems more of an RDF/XML issue than an RDF Concepts issue to me, given that RDF/XML is the one RDF technology that is somewhat likely to be used in conjunction with XML Schema. IMO this further strengthens the argument that a confused user is unlikely to actually find the note; they may or may not be looking in the right spec.)

Best,
Richard
Received on Tuesday, 4 September 2012 11:53:38 UTC

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