# Re: Using cardinality restrictions

From: Uli Sattler <sattler@cs.man.ac.uk>
Date: Tue, 12 Jul 2011 16:34:38 +0100
Cc: <public-owl-dev@w3.org>
Message-Id: <577166F2-B2F0-40F7-A603-9ACA49BB9335@cs.man.ac.uk>

```
On 12 Jul 2011, at 10:27, <Soeren.Kemmann@iese.fraunhofer.de> wrote:

> Hi there,
>
> I’m trying to model (with Protégé 3.4.6 with Pellet Reasoner … just
> in case it matters) that a class A has two subclasses B and C, where
> B and C are disjoint.
> The distinction I want to make is that every instance of A is either
> of subclass B or of C dependent on the cardinality of a property p.
> The “test” is whether the instance has values assigned to property p
> ( p min 1). This kind of works … the instances are interfered to be
> of that type.
> But the other class does not work. If tried (p max 0), (p exactly
> 0), (p exactly 0 RangeClass), but nothing works.
>
> I’m using OWL-DL and as far as I understood 0/1 cardinalities are ok
> for OWL-DL, right?
>

Hi Soeren,

yes, they do - I guess you have, in your ontology, something like

B SubClassOf C
A SubClassOf C  %% these two axioms aren't really necessary if you
have the 2 below...

A EquivalentClass C and (p min 1)
B EquivalentClass C and (p max 0)

...and then when you have an instance of C with

- 1 known p-successor, they are classified as being an instance of A
- no known p-successor, they are ... only classified as being an
instance of C - and you wonder why...

The reason is found in the word 'known' used above: your instance of C
has no *known* p-successor, but could have some, due to the open world
assumption!

So, how to rescue this? For example, you could say explicitly how many
p-successors an individual has...in general, you need a 'closure'
statement that says that the *known* p-successors are all p-successors.

If I remember correctly, the famous Pizza tutorial explains this in
detail (see http://owl.cs.manchester.ac.uk/tutorials/
protegeowltutorial/ )

Cheers, Uli

> Thanks a lot!
> Cheers,
> Sören
>
>
> Dipl. Inf. Soeren Kemmann
> Fraunhofer IESE
> Fraunhofer-Platz 1, 67663 Kaiserslautern, Germany
> Tel.: +49 (0) 631 / 6800 - 2218
> Fax.: +49 (0) 631 / 6800 - 9 2218
> mailto:soeren.kemmann@iese.fraunhofer.de
```
Received on Tuesday, 12 July 2011 15:34:23 UTC

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