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Re: error?

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Wed, 03 Jul 2002 18:12:12 +0100
Message-Id: <5.1.0.14.0.20020703180106.02a44270@15.144.25.13>
To: "Franco Salvetti" <franco.salvetti@tiscalinet.it>, <www-rdf-comments@w3.org>
Cc: <boley@informatik.uni-kl.de>

At 17:07 03/07/2002 +0200, Franco Salvetti wrote:
>Hi,
>
>in the definition of RDFS (official document) there is:
>
><rdf:Property about="http://www.w3.org/1999/02/22-rdf-syntax-ns#object">
>   <rdfs:isDefinedBy 
> rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#"/>
>   <rdfs:label xml:lang="en">object</rdfs:label>
>   <rdfs:comment>The object of an RDF statement.</rdfs:comment>
>   <rdfs:domain 
> rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement"/>
></rdf:Property>
>I see that there is not a statement about that rdfs:range of the property 
>rdf:object. In consideration that the range of a property is the union

The RDFCore WG is modifying the current specs and has resolved that 
multiple range statements have conjunctive semantics, i.e. actual range is 
the intersection of the classes defined in the rdfs:range statements.  This 
is a change from the previous version of the spec.  You can find the latest 
working drafts of the rdf specs linked from the WG overview page at:

   http://www.w3.org/2001/sw/RDFCore/

>  on any single range I think that we can add this two lines at the 
> definition of the property rdf:object
>
>   <rdfs:range rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
>   <rdfs:range rdf:resource="http://www.w3.org/2000/01/rdf-schema#Literal"/>
>
>so that an rdf:object can be either an rdfs:Resource or an rdfs:Literal.

One can think of a range statement as a contraint.  With no range statement 
there is no contraint on the range of rdf:object which is what we want.

>
>A question arise sponteneusly: Can an instance of the class rdfs:Literal 
>be a resource? I hope NO, because the definition of the rdfs:domain of the 
>property rdf:subject is an rdfs:Resource and we know that we cannot have 
>as a subject of an RDF statement a stupid string on characters.

I'm not sure what sense of the term "stupid" can apply to a string of 
characters, but it is currently true that the subject of a statement must 
be a resource.

>  Do am I right?
>
>in
>
><rdf:Property rdf:about="http://www.w3.org/2000/01/rdf-schema#isDefinedBy">
>   <rdfs:isDefinedBy rdf:resource="http://www.w3.org/2000/01/rdf-schema#"/>
>   <rdf:type resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Property"/>
>   <rdfs:subPropertyOf 
> rdf:resource="http://www.w3.org/2000/01/rdf-schema#seeAlso"/>
>   <rdfs:label xml:lang="en">isDefinedBy</rdfs:label>
>   <rdfs:comment>Indicates the namespace of a resource</rdfs:comment>
>   <rdfs:range rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
>   <rdfs:domain rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
></rdf:Property>
>
>it seems to me that there is 2 (two) definition of isDefinedBy in terms of 
>rdf:type.
>
>The first line for me is the same statement than the one in line 3. Am I 
>right?

Yes you are right, there is a redundant statement there.

>
>all the best
>Franco Salvetti
>
>p.s. sorry if I bother you but I'am working on it for my thesis and I see 
>that there are many things not well definited

No bother, thank you for the input.  I hope the answers are clear.  If not, 
please ask again.

Brian

>
Received on Wednesday, 3 July 2002 13:13:14 GMT

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