#32 Problems with negation as failure in Conjunctive Queries

[florianfischer]

Example:
--------
concept Person
concept Animal

relation pet ( ofType Person, ofType Animal)

instance dog memberOf Animal
instance cat memberOf Animal
instance mice memberOf Animal

instance Peter memberOf Person
instance Mary memberOf Person

relationInstance pet(Mary, cat)
relationInstance pet ( Peter, dog )
relationInstance pet(Peter, mice)

The following three queries produce different results:
Query1: ?p memberOf Person and ?a memberOf Animal and naf pet(?p, ?a).
Query2: naf pet(?p, ?a) and ?p memberOf Person and ?a memberOf Animal.
Query2: ?p memberOf Person and naf pet(?p, ?a) and ?a memberOf Animal.

Only no.1 is correct. This behavior becomes apparent in both the wellfounded and stratified evaluation models - so _likely_ the problem is in WSML2Reasoner.