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[DPF] Constraining the use of properties to certain types

From: Keith Waters <kwaters@ftrd.us>
Date: Mon, 6 Jun 2005 12:34:06 -0400
Message-Id: <A7F39E7A-8251-44FE-881E-62EDC96FE8F2@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/

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


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 Monday, 6 June 2005 21:56:09 GMT

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