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Re: Ways to restrict the properties a class may have?

From: Benja Fallenstein <b.fallenstein@gmx.de>
Date: Fri, 29 Oct 2004 13:53:24 +0300
Message-ID: <41822124.8020902@gmx.de>
To: algermissen@acm.org
CC: "www-rdf-interest@w3.org" <www-rdf-interest@w3.org>

Jan Algermissen wrote:
> I know about the various ways to constrain individual properties, but
> I seem to be unable to find out if there is a standard way of restricting
> the set of properties instances of a given class may 'have'.
> (Like relational tables form classes by grouping attributes)

No -- whyever would you want to do that? That would be trying to deprive 
RDF of one of its best features, the ability to extend others' schemas.

Let's say you're modelling a class Employee. Do you believe that you 
should be able to declare which properties an Employee can have? Well, 
an employee is almost certainly a subclass of Person; and if I create a 
x:starsign property on Persons, who are you to decide that Employees 
cannot have this property?

Now, there's a slighly better case if you're modelling an abstract kind 
of entity, such as the relationship between an employee and their 
employer (because an employee can be employed by more than one employer, 
with different salaries etc). But even this kind of resource may have a 
property like rdfs:seeAlso or rdfs:comment, as well as similar 
properties created by third parties, and you shouldn't be able to 
prevent this by saying "here I have ordained the list of all properties 
that instances of this class may possibly have."

- Benja
Received on Friday, 29 October 2004 10:54:04 UTC

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