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[DPF] Constraining the use of properties to certain types

From: Keith Waters <kwaters@ftrd.us>
Date: Wed, 8 Jun 2005 04:00:08 -0400
Message-Id: <DB1EAC24-7111-4929-9D25-0589748C7CD3@ftrd.us>
To: www-di@w3.org

Hi Jeremy and Mark,

This message contains a response to comments on

http://www.w3.org/TR/2004/WD-DPF-20041122/

r7. Constraining the use of properties to certain types
(Open world/closed world issues)

A basic assumption in RDF and OWL is known as the open world assumption.
This is that all descriptions are regarded as incomplete and extensible
in any way not explicitly prohibited.
One of the unfulfilled aspirations of DPF is for some sort
of type constraints in the use of properties. While such constraints
can be expressed in OWL it is quite difficult.
An example of the difficulty can be given using RDFS (which is a subset
of OWL).
In RDFS it is possible to describe the domain of a property (i.e. the
type of resources to which it is applicable) and the range of a property
(i.e. the type of resource which may be the value of that property).
However, a resource can have many types, so that having superficially
conflicting domain and range rules does not actually cause a conflict,
merely multiple typing. So if we had a property that was only applicable
to nokia GPS's and (mis)used it on an ibm gps, we would (unfortunately)
conclude that the ibm gps was also a nokia gps. This can be
addressed in OWL by, in one way or another, saying that no resource
is both an ibm gps and a nokia gps.

For an explanation of the often misunderstood relationship between RDF
Schema, OWL, inference and validation please see
http://esw.w3.org/mt/esw/archives/000048.html

Response:

It is hard to understand precisely what issue is being addressed in  
this comment. The GPS example, with respect to Figure 2 has been  
updated to avoid explicit referencing to GPS and vendors.  
Furthermore, it appears to be about property name conflicts, that are  
not a problem for DPF. Suggesting that we are going to use OWL or RDF  
is incorrect. OWL and RDF are optional implementations for DPF.
-Keith Waters
Received on Wednesday, 8 June 2005 08:01:38 GMT

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