A Semantic Completeness Proof for TaMeD

International audienceDeduction modulo is a theoretical framework designed to introduce computational steps in deductive systems. This approach is well suited to automated theorem proving and a tableau method for first-order classical deduction modulo has been developed. We reformulate this method and give an (almost constructive) semantic completeness proof. This new proof allows us to extend the completeness theorem to several classes of rewrite systems used for computations in deduction modulo. We are then able to build a counter-model when a proof fails for these systems

Deduction modulo theory

This paper is a survey on Deduction modulo theor

Axiom directed Focusing

Long versionInternational audienceSuperdeduction and deduction modulo are methods specially designed to ease the use of first-order theories in predicate logic. Superdeduction modulo, which combines both, enables the user to make a distinct use of computational and reasoning axioms. Although soundness is ensured, using superdeduction and deduction modulo to extend deduction with awkward theories can jeopardize essential properties of the extended system such as cut-elimination or completeness \wrt~predicate logic. Therefore one has to design criteria for theories which can safely be used through superdeduction and deduction modulo. In this paper we revisit the superdeduction paradigm by comparing it with the focusing approach. In particular we prove a focalization theorem for cut-free superdeduction modulo: we show that permutations of inference rules can transform any cut-free proof in deduction modulo into a cut-free proof in superdeduction modulo and conversely, provided that some hypotheses on the synchrony of reasoning axioms are verified. It implies that cut-elimination for deduction modulo and for superdeduction modulo are equivalent. Since several criteria have already been proposed for theories that do not break cut-elimination of the corresponding deduction modulo system, these criteria also imply cut-elimination of the superdeduction modulo system, provided our synchrony hypotheses hold. Finally we design a tableaux method for superdeduction modulo which is sound and complete provided cut-elimination holds

A First-Order Representation of Pure Type Systems Using Superdeduction

International audienceSuperdeduction is a formalism closely related to deduction modulo which permits to enrich a deduction system (especially a first-order one such as natural deduction or sequent calculus) with new inference rules automatically computed from the presentation of a theory. We give a natural encoding from every functional Pure Type System (PTS) into superdeduction by defining an appropriate first-order theory. We prove that this translation is correct and conservative, showing a correspondence between valid typing judgments in the PTS and provable sequents in the corresponding superdeductive system. As a byproduct, we also introduce the superdeductive sequent calculus for intuitionistic logic, which was until now only defined for classical logic. We show its equivalence with the superdeductive natural deduction. This implies that superdeduction can be easily used as a logical framework. These results lead to a better understanding of the implementation and the automation of proof search for PTS, as well as to more cooperation between proof assistants

Linking Focusing and Resolution with Selection

International audienceFocusing and selection are techniques that shrink the proof-search space for respectively sequent calculi and resolution. To bring out a link between them, we generalize them both: we introduce a sequent calculus where each occurrence of an atomic formula can have a positive or a negative polarity; and a resolution method where each literal, whatever its sign, can be selected in input clauses. We prove the equivalence between cut-free proofs in this sequent calculus and derivations of the empty clause in that resolution method. Such a generalization is not semi-complete in general, which allows us to consider complete instances that correspond to theories of any logical strength. We present three complete instances: first, our framework allows us to show that ordinary focusing corresponds to hyperresolution and semantic resolution; the second instance is deduction modulo theory and the related framework called superdeduction; and a new setting, not captured by any existing framework, extends deduction modulo theory with rewriting rules having several left-hand sides, which restricts even more the proof-search space

Automatisation des preuves pour la vérification des règles de l'Atelier B

Cette thèse porte sur la vérification des règles ajoutées de l'Atelier B en utilisant une plate-forme appelée BCARe qui repose sur un plongement de la théorie sous-jacente à la méthode B (théorie de B) dans l'assistant à la preuve Coq. En particulier, nous proposons trois approches pour prouver la validité d'une règle, ce qui revient à prouver une formule exprimée dans la théorie de B. Ces trois approches ont été évaluées sur les règles de la base de règles de SIEMENS IC-MOL. La première approche dite autarcique est développée avec le langage de tactiques de Coq Ltac. Elle repose sur une première étape qui consiste à déplier tous les opérateurs ensemblistes pour obtenir une formule de la logique du premier ordre. Puis nous appliquons une procédure de décision qui met en oeuvre une heuristique naïve en ce qui concerne les instanciations. La deuxième approche, dite sceptique,appelle le prouveur automatique de théorèmes Zenon après avoir effectué l'étape de normalisation précédente. Nous vérifions ensuite les preuves trouvées par Zenon dans le plongement profond de B en Coq. La troisième approche évite l'étape de normalisation précédente grâce à une extension de Zenon utilisant des règles d'inférence spécifiques à la théorie de B. Ces règles sont obtenues grâce à la technique de superdéduction. Cette dernière approche est généralisée en une extension de Zenon à toute théorie grâce à un calcul dynamique des règles de superdéduction. Ce nouvel outil, appelé Super Zenon, peut par exemple prouver des problèmes issus de la bibliothèque de problèmes TPTP.The purpose of this thesis is the verification of Atelier B added rules using the framework named BCARe which relies on a deep embedding of the B theory within the logic of the Coq proof assistant. We propose especially three approaches in order to prove the validity of a rule, which amounts to prove a formula expressed in the B theory. These three approaches have been assessed on the rules coming from the rule database maintained by Siemens IC-MOL. To do so, the first approach, so-called autarkic approach, is developed thanks to the Coq tactic language, Ltac. It rests upon a first step which consists in unfolding the set operators so as to obtain a first order formula. A decision procedure which implements an heuristic is applied afterwards to deal with instantiation. We propose a second approach, so-called skeptic approach, which uses the automated first order theorem prover Zenon, after the previous normalization step has been applied. Then we verify the Zenon proofs in the deep embedding of B in Coq. A third approach consists in using anextension of Zenon to the B method thanks to the superdeduction. Superdeduction allows us to add the axioms of the B theory by means of deduction rules in the proof mechanism of Zenon. This last approach is generalized in an extension of Zenon to every theory thanks to a dynamic calculus of the superdeduction rules. This new tool, named Super Zenon, is able to prove problems coming from the problem library TPTP, for example.PARIS-CNAM (751032301) / SudocSudocFranceF