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Description of rdfs:isDefinedBy in RDF Schema WD

From: Pete Johnston <p.johnston@ukoln.ac.uk>
Date: Fri, 22 Nov 2002 12:50:52 -0000
To: www-rdf-comments@w3.org
Message-ID: <000201c29225$ca8a1f10$2392268a@ulpcpj>


This is really a request for clarification on the descriptions of the
rdfs:isDefinedBy property in


I notice that in the table of "RDF Properties" in the RDF Schema
Overview section (and in the rdfs:comment in the schema in Appendix B),
the description of rdfs:isDefinedBy is:

> Indicates the namespace of a resource

and further down under RDF Utility Classes and Properties:

> The property rdfs:isDefinedBy is a subproperty of rdfs:seeAlso, and
> indicates the resource defining the subject resource.

A while back I asked a question on dc-architecture about the usage of
rdfs:isDefinedBy, and specifically whether rdfs:isDefinedBy could/should
be used to express the relationship between a term and a namespace  


The question spawned a very long debate which I seem to recall spread
across several mailing lists, with opposed views presented, particularly

0&F=&S=&P=805 [Dan Brickley]

which includes

rdfs:isDefinedBy probably should have been called rdfs:ns, since we
added it to RDF Schema as a way of associating a term with the wider
bundle of names it was defined alongside.


0&F=&S=&P=1473 [Patrick Stickler]

which concludes

So the bottom line is that, if you want a property to relate a term to a
specific namespace then you need something other than rdfs:isDefinedBy.
And ideally, you would also instruct every parser to always assert such
statements for every term when parsing. But no existing RDF mechanism
provides for unambiguous preservation of namespace structure.

I tried to follow the ensuing debate as it surfaced in the archive of
the RDF Core WG list, and I think the latest references were in the
thread following

[Dan Brickley]

This message includes the suggestion

For every RDF property there is exactly one correct value for the
rdfs:isDefinedBy property.

When RDF graphs are written in the RDF/XML 1.0 syntax, this value
corresponds to the XML namespace URIref used in the serialized
representation of the RDF properties.

While I must admit this approach rather appealed to me (and I think that
convention is used, for example, in the RDFS representations of the DCMI
vocabularies), I also understand the argument that namespaces do not
exist in RDF and I thought that later contributions on that thread e.g.



reflected opposition to this very "tight" description of
rdfs:isDefinedBy, and it was considered inappropriate to limit
rdfs:isDefinedBy in this way. 

This would seem to be reflected in this message


on the resolution of the issue.

But the text in the recent draft (especially the phrase "Indicates the
namespace of a resource") seems to re-introduce some ambiguity on

(a) the value of rdfs:isDefinedBy is (in all cases?) the XML namespace
URIref used to represent a property in the XML serialization, or 

(b) it is a reference to _any_ resource providing more information
(which _may_ be an XML namespace URIref, which _may_ point to a schema
(an RDF/XML document), but might not be).
Pete Johnston

Pete Johnston 
Interoperability Research Officer 
UKOLN, University of Bath, Bath BA2 7AY, UK 
tel: +44 (0)1225 383619    fax: +44 (0)1225 386838 
Received on Friday, 22 November 2002 08:06:22 GMT

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