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[protege-owl] R: trouble in testing consistency

emanu.storti at tiscali.it emanu.storti at tiscali.it
Wed Oct 1 03:53:04 PDT 2008


--I re-send the message, I hope this time is ok--
Hello, I'm a university student of Computer Engineering. I'm realizing an owl ontology with Protègè 3.3.1.
My problem is to verify whether my ontology is consistent or not.

I have this simple class structure:
owl:Thing
-Algorithm
>>classification_algorithm (with 1 instance: named "a1")
>>clustering_algorithm

-Method
>>classification_method (with 1 instance: "m1")
>>clustering_method (with 1 instance: "m2")
>>da_method (with 1 instance:"m3")

-Task (with 2 instances: "classification" and "feature_selection")


Then, I defined 2 object properties in this way:
uses (domain:Algorithm, range:Method) == an algorithm uses a method
specifies (domain:Method, range:Task) == a method specifies a task

And the connections are:

"m1" specifies "classification"
"m3" specifies "feature_selection"


Well, now I'd like to restrict the property "uses" for class "classification_algorithm", saying that a
classification algorithm MUST use at least 1 method which specifies "classification".

Written in a formal way, in the "asserted condition" Tab of the classification_algorithm class I wrote:

"uses some (Method and (specifies has classification))" as a NECESSARY condition.

1st question: is it syntactically wrong?
2nd question: does it express the correct meaning?


Then, to test the inconsistency, I added this connection:
"c1" uses "m3".
This should not be correct, because an instance of classification_algorithm, according to the restriction, should
"use" an instance of a method which "specify" the "classification" task, and this is not the case, because c1
uses m3, a method which "specify" the "feature_selection" task.

Anyway, Pellet says that the ontology is consistent.
In addition, if I delete at all the connection between the c1 and m3 (so c1 has no connection to any Method), Protégé shows a red square around the "uses" property when I focus on the c1 instance (pointing out that there is an error).
Even in this case, the reasoner says that the ontology is consistent.

3rd question: What's wrong? Doesn't consistency concern this kind of mistakes?
4th question: What kind of ontology test can show me that there is an error?

Thank you in advance,
Emanuele S.


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