Abstract not found

Abstract not found

this paper we overcome these drawbacks by working with clauses with symbolic constraints (Kirchner et al., 1990; Nieuwenhuis and Rubio, 1992; Rubio, 1994; Nieuwenhuis and Rubio, 1995) . A constrained clause C [[ T ]] is a shorthand for the set of ground instances of the clause part C satisfying the constraint T . In a constrained equation

We propose a new inference system for automated deduction with equality and associative commutative operators. This system is an extension of the ordered paramodulation strategy. However, rather than using associativity and commutativity as the other axioms, they are handled by the AC-unification algorithm and the inference rules. Moreover, we prove the refutational completeness of this system without needing the functional reflexive axioms or ACaxioms. Such a result is obtained by semantic tree techniques. We also show that the inference system is compatible with simplification rules.

Abstract not found

. In this paper we solve a long-standing open problem by showing that strict superposition---that is, superposition without equality factoring---is refutationally complete. The difficulty of the problem arises from the fact that the strict calculus, in contrast to the standard calculus with equality factoring, is not compatible with arbitrary removal of tautologies, so that the usual techniques for proving the (refutational) completeness of paramodulation calculi are not directly applicable. We deal with the problem by introducing a suitable notion of direct rewrite proof and modifying proof techniques based on candidate models and counterexamples in that we define these concepts in terms of, not semantic truth, but direct provability. We introduce a corresponding concept of redundancy with which strict superposition is compatible and that covers most simplification techniques. We also show that certain superposition inferences from variables are redundant---a result that is relevant, ...

This paper studies completion in the case of equations with constraints consisting of first-order formulae over equations, disequations, and an irreducibility predicate. We present several inference systems which show in a very precise way how to take advantage of redundancy notions in this framework. A notable feature of these systems is the variety of tradeooes they present for removing redundant instances of the equations involved in an inference. The irreducibility predicates simulate redundancy criteria based on reducibility (such as prime superposition and Blocking in Basic Completion) and the disequality predicates simulate the notion of subsumed critical pairs; in addition, since constraints are passed along with equations, we can perform hereditary versions of all these redundancy checks. This combines in one consistent framework stronger versions of all practical critical pair criteria. We also provide a rigorous analysis of the problem with completing sets of equation...

. The paper investigates reasoning with set-relations: intersection, inclusion and identity of 1-element sets. A language is introduced which, interpreted in a multialgebraic semantics, allows one to specify such relations. An inference system is given and shown sound and refutationally ground-complete for a particular proof strategy which selects only maximal literals from the premise clauses. Each of the introduced set-relations satisfies only two among the three properties of the equivalence relations - we study rewriting with such non-equivalence relations and point out differences from the equational case. As a corollary of the main ground-completeness theorem we obtain ground-completeness of the introduced rewriting technique. 1 Introduction Reasoning with sets becomes an important issue in different areas of computer science. Its relevance can be noticed in constraint and logic programming e.g. [SD86, DO92, Jay92, Sto93], in algebraic approach to nondeterminism e.g. [Hus93, He...

We present a modification to the paramodulation inference system, where semantic equality and non-equality literals are stored as local simplifiers with each clause. The local simplifiers are created when new clauses are generated and inherited by the descendants of that clause. Then the local simplifiers can be used to perform demodulation and unit simplification, if certain conditions are satisfied. This reduces the search space of the theorem proving procedure and the length of the proofs obtained. In fact, we show that for ground SLD resolution with any selection rule, any set of clauses has a polynomial length proof. Without this technique, proofs may be exponential. We show that this process is sound, complete, and compatible with deletion rules (e.g., demodulation, subsumption, unit simplification, and tautology deletion), which do not have to be modified to preserve completeness. We also show the relationship between this technique and model elimination.

. We consider reasoning and rewriting with set-relations: inclusion, nonempty intersection and singleton identity, each of which satisfies only two among the three properties of the equivalence relations. The paper presents a complete inference system which is a generalization of ordered paramodulation and superposition calculi. Notions of rewriting proof and confluent rule system are defined for such nonequivalence relations. Together with the notions of forcing and redundancy they are applied in the completeness proof. Ground completeness cannot be lifted to the nonground case because substitution for variables is restricted to deterministic terms. To overcome the problems of restricted substitutivity and hidden (in relations) existential quantification, unification is defined as a three step process: substitution of determistic terms, introduction of bindings and "on-line" skolemisation. The inference rules based on this unification derive non-ground clauses even from the ground one...