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Re: rdfs:Property rdfs:range questions

From: Murray Spork <m.spork@qut.edu.au>
Date: Tue, 24 Sep 2002 12:30:21 +1000
To: www-rdf-interest@w3.org
Message-id: <3D8FCE3D.3000501@qut.edu.au>

m batsis wrote:
> On Friday 20 September 2002 18:26, SALVETTI FRANCO wrote:
> [...] The rande/domanin are not
> 
>>constraint anymore, but just way to declare the type of a variable. I heard
>>that it could be changed in the future by the W3C.
>>
>>More ore less with this semantic you can say everything in RDF. No
>>constarints!
> 
> 
> Well, it's all about the possible inferences. The term constraint in RDF(S) is 
> simply confusing as DanBri noted.
> 

In light of this discussion - does anyone care to comment on Section 4.3 
of the MT
http://www.w3.org/TR/rdf-mt/#compEntailNote

"For example, one view of domain and range assertions is that they 
should be viewed as constraints on the legality of assertions involving 
a property. On this view, the rules rdfs2 and rdfs3 would be most 
naturally seen as applying 'backwards', and rdfs2 would be better 
phrased as 'If aaa [rdfs:domain] zzz , then if xxx is NOT [rdf:type] 
zzz, then xxx aaa yyy is illegal', and similarly for rdfs3. However, 
this is the same inference, differently phrased, as that expressed by 
the rules in the table above. In other words, these rules should not be 
read as defining only a left-to-right inference pattern. The entailments 
they define can be 'used' in any direction by an inference engine, 
depending on what its task or purpose is. All that the model theory 
defines is the fact of entailment or non-entailment between RDF(S) 
expressions. What use is made of that fact of entailment is up to the 
particular application."

This does appear to me to be a bit confusing - rdfs2 and rdfs3 can be 
used to entail new triples _or_ to make some triples invalid.

Comments?


-- 
Murray Spork
Centre for Information Technology Innovation (CITI)
The Redcone Project
Queensland University of Technology, Brisbane, Australia
Phone: +61-7-3864-9488
Email: m.spork@qut.edu.au
Web: http://redcone.gbst.com/
Received on Tuesday, 24 September 2002 02:43:48 GMT

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