Legal Assessment Using Conjunctive Queries

Using the Web Ontology Language (OWL) for knowledge representation in the legal domain is very promising but has some limitations. The language is complex thus hard to comprehend, still decidability results in a limited expressiveness which may introduce serious problems in modelling. An aspect of limited expressiveness is the tree-model property of OWL, which can be overcome using rule formalisms or introducing variables, however losing decidability is not always acceptable. We propose using conjunctive queries when modelling conditions of legal norms in the HARNESS architecture. Inference services required for modelling legislation and building legal assessment applications can be feasible using grounded queries resulting in a decidable formalism. Since most of the knowledge base remains within the limits of pure OWL2, we can benefit from consistency checking services of OWL2.