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[protege-owl] trouble in testing consistency

emanu.storti at tiscali.it emanu.storti at tiscali.it
Wed Oct 1 03:25:13 PDT 2008


Hello, I'm a university student in Computer Engineering. I'm building 
an owl ontology about algorithms 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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