W3C home > Mailing lists > Public > public-rdf-comments@w3.org > September 2012

Re: Use of XSD namespace in RDF recommendations

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Tue, 04 Sep 2012 15:11:55 +0200
Message-ID: <5045FE1B.1070808@emse.fr>
To: public-rdf-comments@w3.org, richard@ex-parrot.com
FWIW, OWL 2 has a feature to define custom datatypes that can be written 
completely in RDF, without using XML Schema.

Your example for Chapman codes can be written as follows, in Turtle syntax:

@prefix geo: <http://www.example.com/geo#>
@prefix xsd: <http://www.w3.org/2001/XMLSchema#>
@prefix owl: <http://www.w3.org/2002/07/owl#>
@prefix rdfs:<http://www.w3.org/2000/01/rdf-schema#>

geo:chapman-code  a  rdfs:Datatype;
     owl:equivalentClass  [
         a  rdfs:Datatype;
         owl:onDatatype  xsd:string;
         owl:withRestriction ( [xsd:pattern "[a-zA-Z]{3}"] )
     ] .


--AZ


Le 04/09/2012 14:26, Richard Smith a écrit :
>
> Hi Richard,
>
> Richard Cyganiak wrote:
>> Richard Smith wrote:
>
> [snip]
>
>>> <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.
>
> Except that isn't applied uniformly, even amongst the W3
> recommendations. For instance, in section 2.1 of the XML Schema Primer
>
> http://www.w3.org/TR/xmlschema-0/#POSchema
>
> the example begins with
>
> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
>
> and that recommendation uniformly uses 'xsd' as the prefix for the XML
> Schema namespace, without the '#'.
>
> And a google search finds comparably many hits for "xsd:element" and
> "xs:element", so even if using 'xs' is recommended practice, it
> certainly doesn't seem to be established practice.
>
>
>> As far as I know, we have no evidence, and no reason to believe, that
>> this is a common confusion.
>
> Probably not in the form I gave. But the much the same problem manifests
> in a second manner that I hadn't considered when I sent the earlier
> email. I think this is more serious.
>
> The implication of section 5 of the RDF 1.1 Concepts draft is that it
> should be possible to use suitable types from third-party XML Schemas. A
> real example: English counties have a three-letter abbreviation known as
> a Chapman code, and I can define an XML Schema type to represent them. E.g.
>
> <xs:schema xmlns="http://www.w3.org/2001/XMLSchema"
> targetNamespace="http://www.example.com/geo">
> <xs:simpleType name="chapman-code">
> <xs:restriction base="xs:string">
> <!-- I could enumerate them or use a pattern -->
> </xs:restriction>
> <xs:simpleType>
> </xs:schema>
>
> If I want to use this type in RDF, what is its datatype URI? The RDF 1.1
> Concepts draft is silent on the issue. By comparison with XML Schema, we
> might infer that it should be
>
> http://www.example.com/geo#chapman-code
>
> But nothing in the Concepts draft says we should add a '#' in this way.
> And I am aware of nothing in the XML Schema recommendations that defines
> the notion of a datatype URI for a schema type.
>
> And if we do add the '#', do we still do this if the XML Schema
> targetNamespace already ends with a '#'? Or with a '/'?
>
>> (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.
>
> I'm not sure I agree. In some ways, I think RDFa is the most likely
> technology to be used within an XML Schema.
>
> Richard
>
>

-- 
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/
Received on Tuesday, 4 September 2012 13:12:28 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 20:29:54 UTC