[Pellet-users] Problems with Pellet and DIG

[Evren Sirin]

This is a common misconception about OWL not having Unique Name 
Assumption (UNA) and having Open World Assumption (OWA). With no other 
information, there is no reason to infer individuals B, C, D, and E are 
different from each other. for this reason,  all we can infer is A has 
at least one PhD but for all we know B, C, D, and E could all be 
different names for the same individual. THat is why A will not be 
inferred to be an instance of the min cardinality restriction.

In OWL, you would use owl:differentFrom or owl:AllDisjoint statements to 
declare the distinctness of those individuals. I don't know for sure but 
I believe there is no corresponding statement in DIG (one of many 
insufficiencies of DIG).

Pellet provides a configuration option to turn on UNA so every named 
individual is treated distinct and you would get your expected result. 
See [1] for details about this option.

Cheers,
Evren

[1] http://pellet.owldl.com/faq/una/




On 5/17/08 8:23 AM, michele.baggi at dimi.uniud.it wrote:
> Hallo,
> I'm a PhD student at the University of Siena - Italy and I'm using the
> Pellet reasoner for a projet of semantic filtering of XML documents. To
> interface Pellet I use the DIG Interface 1.0, but I noticed a problem with
> the number restriction construct, when querying a loaded ontology.
>
> I loaded the following ontology:
> Concepts: Prof, PhD
> Individuals: A, B, C, D, E
> Instances: A -> Prof,   B, C, D, E -> PhD
> Role: hasPhd
> Associations: hasPhD(A, B), hasPhD(A, C), hasPhD(A, D), hasPhD(A, E).
>
> In attachment there is a file containing the DIG Tell statement for the
> ontology I just here briefly described.
>
> I tried to query this ontology using the following DIG ask statement:
>
> <asks xmlns= ... >
>   <instance id="example1">
>     <individual name="A"/>
>     <and>
>      <catom name="Prof"/>
>      <atleast num="3">
>        <ratom name="hasPhD"/>
>        <catom name="PhD"/>
>      </atleast>
>     </and>
>   </instance>
> </asks>
>
> which asks for individual instances of concept "Prof" which are related to
> at least 3 individual instances of concept "PhD",
> and I get an empty list as answer, while I think it will return the
> individual "A".
>
> Any suggestion will be appreciated,
> I wish everybody a good weekend.
> Michele
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