부산대학교 도서관

We solve a problem, stated in [5] , showing that Sticky Datalog ∃ , defined in the cited paper as an element of the Datalog ± project, has the Finite Controllability property, which means that whenever a query Ψ is not logically implied by a set of atoms D and a Sticky Datalog ∃ theory T a finite structure M can be found such that M ⊨ D , T , but M ⊭ Ψ . In order to do that, we develop a technique, which we believe can have further applications, of approximating C h a s e ( T , D ) , for a database instance D and a set of tuple generating dependencies and Datalog rules T , by an infinite sequence of finite structures, all of them being models of T and D . [ABSTRACT FROM AUTHOR]