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schneidt at cs.man.ac.uk
Fri Jan 15 01:08:32 PST 2010
On 14 Jan 2010, at 19:59, Thomas Russ wrote:
> I don't normally use Protege 4, so I'm not the best person to answer
> some of these.
> On Jan 14, 2010, at 3:09 AM, Poovendran Moodley wrote:
>>> As a simple example, if you define a class
>>> 50-year-old == Person and (hasValue age 50)
>> I wasn't sure if age should be an object or data property. So I
>> tried both: as a data property, Bill was inferred as a 50-year-old,
>> where the class 50-year-old has the equivalence class "Person and
>> (age value 50)." However, Fred was not inferred to have the data
>> property of age being 50 (though Fred, of course was inferred to be
>> a Person since 50-year-old is-a Person).
> I'm not sure where you would have to look to find inferred datatype
> property values using Protege 4.0, but I would expect them to be
> available somewhere.
Hmm, this is a bit tricky: since most datatypes are infinite, a GUI
that displays inferred datatype values of individuals would have to
handle an infinite search space. However, if you specify the value
you're after, the DL query tab of Protégé 4 will give you the required
answer. Specify the class expression "age value 50" as the query, tick
the box "Individual", and hit "Execute". The answers under "Instances"
will include Fred.
>>> You can then make the following assertions:
>>> Fred type 50-year-old
>>> Bill type Person
>>> Bill age 50
>>> Bill will be recognized as belonging to the class "50-year-old".
>>> Fred will have an inferred property value for "age" of 50.
>>> Where the difference becomes apparent and will diverge from what
>>> you might get from an object-oriented perspective is if you use
>>> some of the other restrictions. Most interesting would be, for
>>> example the "allValuesFrom" or the "minCardinality" restrictions.
>>> In Protege 4, the class expression editor doesn't support the
>>> keywords allValuesFrom or minCardinality. I think I managed to try
>>> out using allValuesFrom but I'm not sure how to express
> I think Protege 4 normally uses the more abbreviated Manchester
> syntax. In that case
> allValuesFrom = only
> minCardinality = min
> There is a nice summary table at http://www.co-ode.org/resources/reference/manchester_syntax/
>>> If you were to define
>>> A == B and (allValuesFrom P 50-year-old)
>> I used that class A has the equivalence class: B and (P only 50-
>> year-old). Indeed, i-2 was inferred to be of type 50-year-old. It
>> didn't gain the data property age 50 but if I used the other
>> 50YearOld class in the equivalence class (described above) then i-2
>> did get the "hasValue 50" object property inference as expected.
> Sounds like the same issue as above.
>>> and then assert
>>> i-1 type A
>>> i-1 P i-2
>>> then the inference engine will conclude that i-2 must be of type
>>> 50-year-old, and that information will be available for further
>>> reasoning. In particular, the reasoner will figure out that the
>>> age of i-2 must be 50.
>>> Instead, if you were to define
>>> X = Y and (minCardinality P 3)
>> I suspected that the keyword only could mean allValuesFrom, and it
>> seemed to work as such. I suspect that the keyword min means
>> minCardinality but I'm unable to construct a valid expression in
>> Protege. I'd love to know how it's done :D
> Correct on the keyword correspondences. I think the form you need
> is "P min 3".
>> and then assert
>> i-3 type X
>> then the reasoner will conclude that i-3 has at least 3 values for
>> property P, but it won't be able to tell you which ones they are.
>> This is where open world reasoning comes into play. Even though
>> there are 3 fillers, they don't have to be specifically
>> identified. OWL is quite able to reason with just this partial
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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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