Implication and Axiomatization of Functional Constraints on Patterns with an Application to the RDF Data Model

Abstract

Akhtar et al. introduced equality-generating constraints and functional constraints as an initial step towards dependency-like integrity constraints for RDF data [1]. Here, we focus on functional constraints. The usefulness of functional constraints is not limited to the RDF data model. Therefore, we study the functional constraints in the more general setting of relations with arbitrary arity. We show that a chase algorithm for functional constraints can be normalized to a more specialized symmetry-preserving chase algorithm. This symmetry-preserving chase algorithm is subsequently used to construct a sound and complete axiomatization for the functional constraints. This axiomatization is in particular applicable in the RDF data model, solving a major open problem of Akhtar et al.