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# [protege-owl] Enumerated Classes and Special Relationships

Thomas Schneider schneidt at cs.man.ac.uk
Mon Jan 25 01:06:48 PST 2010

```Hi Pooven,

On 22 Jan 2010, at 09:47, Poovendran Moodley wrote:

> [...] So I've read the material you've suggested (so grateful for
> the link!!) and it was just what I was looking for. The paper was a
> bit difficult for me to understand but the presentation was clear.
> They suggest using an intermediate individual to allow, what they
> call, a concept product - aptly named.
>
> So they suggest (on page 9 of the presentation) the use of roles R1
> and R2 such that for A: R1 value x, and for B: R2 value x. Then R
> can be defined to be the superclass of R1 ◦ Inv(R2). I'm not sure
> what ◦ is suppose to mean but I've interpreted it as R being
> equivalent to both R1 and Inv(R2) and, the subclass of these object
> properties. I also made Inv(R2) transitive and the reasoner infers
> that every individual in A has role R with every individual in class
> B.

No, the circle denotes the concatenation of roles or, in OWL speak, an
object property chain. The axiom "R1 o Inv(R2) subPropertyOf R" means
that whenever an individual x has some individual y as R1-value and y
has z as Inv(R2)-value, then x has z as R-value. Your modelling says
something different.

> While it does give me the results I was searching for, are there any
> shortcomings or reservations that I should be aware of? I was
> thinking of a transitive role and an intermediate individual but
> wasn't sure if it made sense to model knowledge in that way... but
> it seems it's an effective work around :)

Well, if you use the solution as given in the paper, you might have to
take care that the global restrictions on axioms in OWL 2 DL [1]
aren't violated when you use the roles R, R1, R2 in other axioms.

Cheers

Thomas

[1] http://www.w3.org/TR/owl2-syntax/#Global_Restrictions_on_Axioms_in_OWL_2_DL

>
> Kind regards
> Pooven
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+----------------------------------------------------------------------+
|  Dr Thomas Schneider                    schneider (at) cs.man.ac.uk  |
|  School of Computer Science       http://www.cs.man.ac.uk/~schneidt  |
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