Type inference for datalog with complex type hierarchies

Abstract

Type inference for Datalog can be understood as the problem of mapping programs to a sublanguage for which containment is decidable. To wit, given a program in Datalog, a schema describing the types of extensional relations, and a user-supplied set of facts about the basic types (stating conditions such as disjointness, implication or equivalence), we aim to infer an over-approximation of the semantics of the program, which should be expressible in a suitable sublanguage of Datalog.