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Re: Container in RDF Schema

From: Andrei S. Lopatenko <andrei@derpi.tuwien.ac.at>
Date: Mon, 6 Aug 2001 17:57:40 +0200
Message-ID: <009201c11e90$85890d40$a6498280@tuwien.ac.at>
To: (wrong string) çois Leygues" <francoisleygues@yahoo.com>
Cc: <www-rdf-interest@w3.org>
Thank you, François
I've read paper McBride, Beckett,
but did not know about decisions of 29th June RDF WG meeting.
So
"On 29th June 2001, the WG decided that containers will match the typed node
production in the grammar (M&S Section 6, production 6.13) and that the
container specific productions (productions 6.25 to 6.31) and any references
to them be removed from the grammar. rdf:li elements will be translated to
rdf:_nnn elements when they are found matching either a propertyElt
(production 6.12) or a a typedNode (production 6.13). The decision includes
a set of test cases."
I would like to check
if rdf:_nnn elements are instances of ...  what?
It is not clear from
http://www-uk.hpl.hp.com/people/bwm/rdf/issues/containersyntax/current.htm,
http://www.w3.org/2000/03/rdf-tracking/#rdf-containers-syntax-ambiguity
I suppose they are instances of rdf:li? (where
rdf=http://www.w3.rg/.../rdf-syntax-ns#)
So if I would like to define class project with a list of
project-participator
is it right way (in pure RDF Schema without any DAML)? (Yes, I agree that
your suggestion is correct but is following right from new point of view? )
<rdfs:Class rdf:ID="Project">
  <rdfs:subClassOf rdf:resource="#Resource"/>
</rdfs:Class>
<rdf:Property rdf:ID="project-participators">
    <rdfs:domain rdf:resource="Project">
    <rdfs:range rdf:resource="project-participator">
    <rdfs:subClassOf rdf:resource="rdf:Bag"/>
</rdf:Property>
<rdfs:Class rdf:ID="project-participator">
  <rdfs:subClassOf rdf:resource="rdf:li"/>
</rdfs:Class>
<rdf:Property rdf:ID="proj_part_role">
    <rdfs:domain rdf:resource="project-participator">
</rdf:Property>
<rdf:Property rdf:ID="proj_part_person">
    <rdfs:domain rdf:resource="project-participator">
</rdf:Property>



----- Original Message -----
From: "François Leygues" <francoisleygues@yahoo.com>
To: <www-rdf-interest@w3.org>
Cc: <andrei@derpi.tuwien.ac.at>
Sent: Sunday, August 05, 2001 10:11 PM
Subject: Re: Container in RDF Schema


> Aaron Swartz wrote:
> >
> > On Friday, July 27, 2001, at 05:46  AM, Andrei S.
> Lopatenko wrote:
> >
> > > But how to say that it is a Bag of person-project?
> >
> > This is a known issue:
> >
> >
> http://www.w3.org/2000/03/rdf-tracking/#rdfs-constraining-containers
>
> A) Yes it is but now things have been vastly improved.
> It is now possible to
> use rdf:li with any resource, which allows containers
> to be subclassed (BRAVO!!!)
>
> This recent decision
> (http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Jun/0520.html)
> is already implemented in the new RDF parser from HP
> (http://www-uk.hpl.hp.com/people/jjc/arp/index.html).
>
> B) However, there is no generally accepted way to
> cleanly constrain containers.
> I have already suggested to use a "metaclass" based
> solution, which
> could be described by :
>    * a class ConstrainedContainer
>    * a property containerConstraint
>
> @prefix : <#>.
>
> :ConstrainedContainer a rdfs:Class;
> rdfs:subClassOf rdfs:Class.
> :containerConstraint a rdf:Property;
> rdfs:domain :ConstrainedContainer;
> rdfs:range rdfs:Class.
>
> Let's define a constrained container :
>
> :LiteralSeq a :ConstrainedContainer;
> rdfs:subClassOf rdfs:Seq;
> :containerConstraint rdfs:Literal
>
> Lets use it:
>
> :MySeq a :LiteralSeq;
> rdf:li "this";
> rdf:li "is";
> rdf:li "a sequence".
>
> Why not define cardinality constraints ?
>
> We could add additional properties :
>
> @prefix xsd: <http://www.w3.org/2000/10/XMLSchema#>
>
> (containerCardinality containerMaxCardinality
> containerMinCardinality )
> a rdf:Property;
> rdfs:domain :ConstrainedContainer;
> rds:range xsd:nonNegativeInteger.
>
> :LiteralSeq would be protected agains emptyness by :
>
> :LiteralSeq :containerMinCardinality 1.
>
> C) This approach is similar to DAML:
>
> @prefix daml: <http://www.daml.org/2001/03/daml+oil#>
> @prefix xsd: <http://www.w3.org/2000/10/XMLSchema#>
>
> daml:Class a rdfs:Class;
> rdfs:subClassOf rdfs:Class
>
> Which is precisely a metaclass...
>
>
> daml:Restriction a rdfs:Class;
> rdfs:subClassOf daml:Class.
>
> which is another metaclass, and  with:
>
> onProperty a rdf:Property;
> rdfs:domain daml:Restriction;
> rdfs:range rdf:Property.
>
> it is possible to define a whole set of cardinality
> constraints :
>
> daml:cardinality a rdf:Property;
> rdfs:domain daml:Restriction;
> rdfs:range xsd:nonNegativeInteger.
>
> daml:maxCardinality a rdf:Property;
> rdfs:domain daml:Restriction;
> rdfs:range xsd:nonNegativeInteger.
>
> daml:minCardinality a rdf:Property;
> rdfs:domain daml:Restriction;
> rdfs:range xsd:nonNegativeInteger.
>
> This is used in a rather complex way:
>
> :Person a daml:Class ;
> rdfs:subClassOf [
> a daml:Restriction;
> daml:cardinality "1";
> daml:onProperty ":hasFather";
> ].
> with:
>
> :hasFather a rdf:Property ;
> rdfs:domain :Person;
> rdfs:range :Person.
>
> This express a nice, but complex, restriction in the
> usage of a property WHEN it is used on a given class.
>
> Note that the cardinality constraints in daml applies
> only to specific properties, not on containers...
> Of course, there are the daml collections but...
>
> D) there is a suggestion (
> http://lists.w3.org/Archives/Public/www-rdf-interest/2001Jul/0094.html
> ) to kill the container notion. I dont like it,
> because it changes RDF too much...
>
>
> E) In conclusion, several queries :
>
> 1) what is the exact status of DAML according to RDF
> Schema ?
> -should we adopt daml and use it , including the
> daml:collection parseType?
> -is it reasonable or foolish  to reinvent other
> conventions ?
> -are RDF containers deprecated ?
>
> 2) Why not completing RDF Schema with the minimum
> necessary to :
> - constrain containers member types?
> - constrain containers cardinalities ?
>
> 3) Please, continue to save RDF containers !
>
>
> Bye.
>
>
>
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Received on Monday, 6 August 2001 11:52:30 GMT

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