W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > April 2002

Re: Range constraints on collection members

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Fri, 5 Apr 2002 18:35:57 -0600
Message-Id: <p05101514b8d3ef2fdce2@[65.217.30.94]>
To: Patrick Stickler <patrick.stickler@nokia.com>
Cc: w3c-rdfcore-wg@w3.org
>On 2002-04-04 22:51, "ext Graham Klyne" <Graham.Klyne@MIMEsweeper.com>
>wrote:
>
>>  At 06:02 PM 4/4/02 +0100, Brian McBride wrote:
>>>  RDF Schema Issues
>>>
>>>      * rdfs-constraining-containers: Should it be possible to constrain
>>>  the members of a container to be of a given type?
>>
>>  I have a vague recollection we'd decided to defer this one??  (i.e. that
>>  RDFS 1.0 would provide no such capability.)
>
>I just recieved email from an implementor, Garret Wilson at Global Mentor,
>that this is sorely needed for what they are doing.

Then maybe they should be using DAML ? Look, RDF is a simple 
language. Various people will definitely want more than RDF can 
provide. We cannot insert new features just because they are needed: 
then we really would be doing Web Logic, as Massimo has accused us of 
doing.

>I encouraged him to post a summary of the issue to RDF comments.
>
>My present take on this is that we need an additional constraint
>property that applies to containers, such as rdfs:containerRange
>which would be used in conjunction with rdfs:range.
>
>We can't simply extend the semantics of rdfs:range to collections
>because one may wish to say that a property must take a collection,
>not just a single value, and thus, rdfs:range breaks. What is
>needed is an additional constraint mechanism, such as something
>like rdfs:collectionRange which would apply to the members of
>a collection. One would then specify e.g. that the property's
>rdfs:range would be rdf:Bag and the rdfs:collectionRange would
>be xsd:string, etc.

We could add this, but its not clear what it would do to the 
semantics. I have an uneasy feeling that it might be quite 
complicated. This is a limited kind of a restriction-on-property (the 
container is restricted to things that have the appropriate range 
property) and that seems to rather go beyond RDFS.

Pat
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Received on Friday, 5 April 2002 19:40:00 EST

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