Hi all,
I am new to this list and am hoping to get some general advice with
regards to modeling knowledge in OWL. I hope that this is an appropriate
venue, it was suggested to me for just this sort of inquiry. (01)
Suppose, for the sake of discussion, we have an OWL property
:has_committee_member, and that we want to say that a committee is never
a committee if it doesn't have at least 2 member. That is, we want to
say that, irrespective of where it is used, the property
:has_committee_member has min cardinality of 2. Now, we might say: (02)
:EmployeeReviewBoard rdfs:subClassOf (:has_committee_member
owl:minCardinality 5) (03)
That is, an employee review board refines the restriction to say that,
not only must the cardinality be 2 or greater, in fact it must be 5 or
greater. (04)
This latter statement is easy enough to express in OWL, just as we did
above. But the former statement, that the property has a min cardinality
no matter where it is used is trickier. I could do it like this: (05)
owl:Thing rdfs:subClassOf (:has_committee_member owl:minCardinality 2) (06)
But is it possible to do it without invoking a class. For example, I can
say that a property is functional, or I can assert its range, without
invoking owl:Thing. Can I do the same for min and max cardinality? I
tried the following (seemingly circular) assertion and I'm wondering if
it is valid (modified and simplified to suit this example): (07)
<owl:ObjectProperty rdf:about="...#has_committee_member">
...
<rdfs:domain>
<owl:Restriction>
<owl:onProperty rdf:resource="...#has_committee_member"/>
<owl:minCardinality
rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger";>2</owl:maxCardinality>
</owl:Restriction>
</rdfs:domain>
</owl:ObjectProperty> (08)
Or written another way: (09)
:has_committee_member rdfs:domain (:has_committee_member
owl:minCardinality 2) (010)
What do you think? Protege doesn't complain, but actually uses owl:Thing
in its display of the above representation. So, it may be deciding that
it is equivalent to invoking the class? (011)
--
Landon Todd Detwiler
Structural Informatics Group (SIG)
University of Washington (012)
phone: 206-616-2336 (013)
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