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Re: Comments on informal meaning of the RDFS vocabulary

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 29 Jan 2003 07:01:16 -0500 (EST)
Message-Id: <20030129.070116.65662896.pfps@research.bell-labs.com>
To: bwm@hplb.hpl.hp.com
Cc: www-rdf-comments@w3.org

From: Brian McBride <bwm@hplb.hpl.hp.com>
Subject: Re: Comments on informal meaning of the RDFS vocabulary
Date: Wed, 29 Jan 2003 10:06:40 +0000

> At 13:19 28/01/2003 -0500, Peter F. Patel-Schneider wrote:
> >The RDF Schema document provides intended meanings for some of the RDFS
> >vocabulary that is not supported by the RDF Semantics.  Vocabulary that
> >fits into this category includes rdfs:label and rdfs:comment.
> I need something a bit more specific to go on here.  Please can provide a 
> URI reference to the problematic text in the schema document and state 
> clearly what the issue is.  In the interests of economy of effort, an 
> example explained in detail and a list of "similarly for" would work.

Well, I don't think that text has URI references, but I can certainly
provide examples.

> >   The
> >distinction between these meanings and the meanings supported by the RDF
> >semantics, such as for rdfs:subClassOf, needs to be stated much more
> >clearly.
> Again, can you be more specific about the difference you refer to.

Consider the following three examples (slightly reformatted but otherwise

	rdf:type is an instance of rdf:Property that is used to state that
	a resource is an instance of a class.  A triple of the form:
		R rdf:type C
	states that C is an instance of rdfs:Class and R is an instance of C.

	rdf:first is an instance of rdf:Property that is used to indicate
	the first item of a list.  A triple of the form:
		L rdf:first O
	states that L is an instance of rdf:List and that O is the first
	item of the list. 

	rdfs:label is an instance of rdf:Property that is used to provide a
	human-readable version of a resource's name.  A triple of the form:
		R rdfs:label L
	states that L is a human readable label for R.

There is essentially no difference between the way these three are worded.
However, the first (rdf:type) is a fundamental part of the semantics of
RDF.  There are semantic conditions in RDF that make the description above
for rdf:type part of the very meaning of RDF.  The second (rdf:first) and
third (rdfs:label), on the other hand, have a very different status.  There
are no semantic conditions that force the descriptions above for these two
vocabulary elements to play the roles given for them.

> >This is particularly important because of the notion of social meaning in
> >RDF.  Without a clear distinction, the reader can be left with the
> >impression that there is no difference between social meaning and model
> >theory meaning.
> Ah, right, I think I see the trend of what you are getting at here, but I 
> still need a clearer statement of what the issues are.

The lack of a distinction in the wording describing rdf:type and rdfs:label
takes part of the social meaning that is being promoted for RDF (i.e., the
social meaning of rdfs:label) and tries to give it the same status as the
model theory meaning.

> Brian

Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies
Received on Wednesday, 29 January 2003 07:01:33 UTC

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