Re: Properties of Properties Question

From: "Hart, Lewis" <lhart@grci.com>
Subject: Property's of Properties Question
Date: Mon, 22 Oct 2001 16:07:47 -0400

> A simple question, with hopefully a simple answer. Is it possible to place a
> restriction on the property of a property in DAML[+OIL]? 

No.  At least I don't think so.  Certainly not in general.  

> What I would like to say, for example is:
>  
> <daml:ObjectProperty rdf:ID='Foo'>
>     <daml:subPropertyOf>
>         <daml:Restriction>
>             <daml:onProperty rdf:resource='#Bar'/>
>             <daml:toProperty rdf:resource='#Baz'/>
>         </daml:Restriction>
>     </daml:subPropertyOf>
> </daml:ObjectProperty rdf:ID='Foo'>
>  
> Except for the fact that daml:Restriction is a daml:Class and
> daml:toProperty doesn't exist, this would be fine. 

If you have to use except, it isn't DAML+OIL.  :-)
daml:Restriction forms a daml:Class, which is not really suitable as the
superproperty of a property.

All that said, RDF allows entities to be both classes and properties, so
what you are doing above is to
1/ create an unnamed class with a malformed restriction, which means that
   there will be no semantic constraints for the class
2/ assert that Foo is a subproperty of the property that has the same
   identity as the class

So you have said roughly the same thing as 

 <daml:ObjectProperty rdf:ID='Foo'>
     <daml:subPropertyOf>
         <rdf:Property />
     </daml:subPropertyOf>
 </daml:ObjectProperty rdf:ID='Foo'>

as far as DAML+OIL is concerned.

> Thanks - Lewis

I don't think that you can do what you want.  However, if you give a
concrete example, I would be able to tell for sure.

Peter F. Patel-Schneider
Class of '72, GRCI

Received on Monday, 22 October 2001 16:32:08 UTC