ISALOG- : A Deductive Language with Negation for Complex-Object Databases with Hierarchies

The IsaLog: model and language are presented. The model has complex objects with classes, relations, and isa hierarchies. The language is strongly typed and declarative. The main issue is the de nition of the semantics of the IsaLog: language. The novel features are mostly due to the interaction of hierarchies with negation in the body of rules. Two semantics are presented and shown to be equivalent: a strati ed semantics based on an original notion of strati cation, needed in order to correctly deal with hierarchies, and a reduction to logic programming with function symbols. The solutions are based on a new technique (explicit Skolem functors) that provides a powerful tool for manipulating object identi ers.