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Re: Meta-classes? (layered architecture)

From: Je'ro^me Euzenat <Jerome.Euzenat@inrialpes.fr>
Date: Fri, 20 Oct 2000 12:39:25 +0200
Message-Id: <p04310102b6150fdbaa42@[194.199.22.158]>
To: Dan Connolly <connolly@w3.org>
Cc: www-rdf-logic@w3.org
Hello,

In his message (Re: Meta-classes? (layered architecture)) of 18/10/00,
Dan Connolly wrote:
>Ian Horrocks wrote:
>  > In OIL, it was explicitly decided that, in the base language, the
>>  denotation of classes and relations should be sets of objects and
>>  binary relations between objects, and that meta-extensions, if
>>  required, would be provided in additional language layers (yet to be
>>  defined). The rationale behind this layered architecture is that we
>>  should extend RDFS in relatively small increments (in the same way
>>  that RDFS is a small increment w.r.t. RDF).
>
>In this sense, I don't view RDFS as an extension to RDF;
>that is: a document that uses terms from the RDFS
>vocabulary is still an RDF document. RDFS is,
>in this sense, more of an application of RDF than
>an extension of it... just like XHTML is an application
>of XML, not an extension of it.

This is not very true. In XHTML you cannot describe the structure of 
an XML document like in RDFS (resp. XML-Schema) you can describe the 
structure of the
RDF (resp. XML) documents, including themselves.
So, RDFS is an application of RDF.
But RDFS is more than that, and expecially, it is supposed to have 
that reflexivity property: it describes itself.
I am not sure that this makes RDFS an extension of RDF? I am puzzled, 
I would say that Schemas are not at the same level. But, with this 
reflexivity property, the levels tend to vanish (where is the neater 
time of DTDs ;-).
-- 
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Received on Friday, 20 October 2000 06:40:31 GMT

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