A Hybrid System with Datalog and Concept Languages

We present a hybrid system for knowledge representation, called \(\mathcal{A}\mathcal{L}\)-log, based on the concept language \(\mathcal{A}\mathcal{L}\mathcal{C}\) and the deductive database language Datalog. \(\mathcal{A}\mathcal{L}\)-log embodies two subsystems, called structural and relational. The former allows for the definition of structural knowledge about the classes of interest and the membership relation between objects and classes. The latter allows for the definition of relational knowledge about the objects described in the structural component. The interaction between the two components is obtained by allowing \(\mathcal{A}\mathcal{L}\mathcal{C}\)-constraints within Datalog clauses, thus requiring the variables in the clauses to range over the set of instances of a specified concept. We propose a method for hybrid reasoning based on constrained resolution, where the usual deduction procedure defined for Datalog is integrated with a method for reasoning on the structural knowledge.