Towards a Type Discipline for Answer Set Programming

Abstract

Abstract. We argue that it is high time that types had a beneficial impact in the field of Answer Set Programming and in particular Disjunctive Datalog as exemplified by the DLV system. Things become immediately more challenging, as we wish to present a type system for DLV-Complex, an extension of DLV with uninterpreted function symbols, external implemented predicates and types. Our type system owes to the seminal polymorphic type system for Prolog introduced by Mycroft and O'Keefe, in the formulation by Lakshman and Reddy. The most innovative part of the paper is developing a declarative grounding procedure which is at the same time appropriate for the operational semantics of ASP and able to handle the new features provided by DLV-Complex. We discuss the soundness of the procedure and evaluate informally its success in reducing, as expected, the set of ground terms. This yields an automatic reduction in size and numbers of (non isomorphic) models. Similar results could have only been achieved in the current untyped version by careful use of generator predicates in lieu of types.

Applying ASP to UML Model Validation

“…In particular, obj(C) is the type of the oids for a class type C and association(C1,C2) the type of the associations between class C1 (left hand side) and C2 (right hand side). For the sake of type safe grounding [5], every ground term must have a unique type. To this aim, [5] introduces annotated functions f J (.…”

“…For the sake of type safe grounding [5], every ground term must have a unique type. To this aim, [5] introduces annotated functions f J (. .…”

“…the snapshots in the same format. The main theoretical contribution consists in a specialized representation of UML class diagrams into DLV-Complex, tailored to the fully automatic generation of non isomorphic snapshots The representation makes essential use of DLV-Complex's external functions, but still requires the introduction of an intermediate language (DLVExi) adding polymorphic types and existential quantification [5].…”