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In this paper, we present an extension of the scheme HH(C) (Hereditary Harrop formulas with Constraints) with a suitable formulation of negation in order to obtain a constraint deductive database query language. In addition to constraints, our proposal includes logical con-nectives (implication and quantifiers) for defining databases and queries, which(More)
This paper is focused on a double extension of traditional Logic Programming which enhances it following two different approaches. On one hand, extending Horn logic to hereditary Harrop formulas (HH), in order to improve the expressive power; on the other, incorporating constraints, in order to increase the efficiency. For this combination, called HH(C), an(More)
We propose a sound and complete free variable semantic tableau method for handling many-sorted preorders in a rst order logic, where functions and predicates behave monotonically or antimonotonically. We formulate additional expansion tableau rules as a more eecient alternative to adding the axioms characterizing a preordered structure. Completeness of the(More)
Combining the logic of hereditary Harrop formulas HH with a constraint system, a logic programming language is obtained that extends Horn clauses in two different directions, thus enhancing substantially the expressivity of Prolog. The implementation of this new language requires the ability to test the satisfiability of constraints built up by means of(More)
In the same way that Datalog and Datalog with constraints arise when modelling databases inspired on Prolog and CLP (Constraint Logic Programming), respectively , we introduce the constraint logic programming scheme HH(C) (Hereditary Harrop formulas with Constraints) as the basis for a database language. We show that HH(C) can fulfill all relational algebra(More)
Combining the logic of hereditary Harrop formulas HH with a constraint system , a logic programming language is obtained that extends Horn clauses in two different directions, thus enhancing substantially the expressivity of Prolog. This new language is parametric over the constraint system. A constraint solver for a particular instance will test the(More)
Constraint Logic Programming (CLP) and Hereditary Harrop Formulas (HH)are two well known ways to enhance the expressivity of Horn clauses. In this paper, we present a novel combination of these two approaches. We show how to enrich the syntax and proof theory of HH with the help of a given constraint system, in such a way that the key property of HH as a(More)