Olivier Gasquet

Olivier Gasquet
IRIT / Paul Sabatier University - Toulouse III

Professor

About

54
Publications
3,893
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469
Citations
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September 1995 - present
Paul Sabatier University - Toulouse III
Position
  • Professor (Full)

Publications

Publications (54)
Conference Paper
This work deals with logical formalization and problem solving using automated solvers. We present the automatic translator TouIST that provides a simple language to generate logical formulas from a problem description. Our tool allows us to model many static or dynamic combinatorial problems and to benefit from the regular improvements of SAT, QBF...
Conference Paper
This work deals with logical formalization and problem solving using automated solvers. We present the automatic translator TouIST that provides a simple language to generate logical formulas from a problem description. Our tool allows us to model many static or dynamic combinatorial problems and to benefit from the regular improvements of SAT, QBF...
Article
Considerable improvements in the technology and performance of SAT solvers has made their use possible for the resolution of various problems in artificial intelligence, and among them that of generating plans. Recently, promising Quantified Boolean Formula (QBF) solvers have been developed and we may expect that in a near future they become as eff...
Article
Considerable improvements in the technology and performance of SAT solvers has made their use possible for the resolution of various problems in artificial intelligence, and among them that of generating plans. Recently, promising Quantified Boolean Formula (QBF) solvers have been developed and we may expect that in a near future they become as eff...
Article
Full-text available
We consider multi-agent scenarios where each agent controls a surveillance camera in the plane, with fixed position and angle of vision, but rotating freely. The agents can thus observe the surroundings and each other. They can also reason about each other’s observation abilities and knowledge derived from these observations. We introduce suitable...
Article
Full-text available
SAT provers are powerful tools for solving real-sized logic problems, but using them requires solid programming knowledge and may be seen w.r.t.\ logic like assembly language w.r.t.\ programming. Something like a high level language was missing to ease various users to take benefit of these tools. {\sc \texttt {TouIST}}\ aims at filling this gap. I...
Technical Report
Full-text available
We consider multi-agent scenarios where each agent controls a surveillance camera positioned in the plane, with fixed po-sition and angle of view, but rotating freely. The agents can thus observe the surroundings and each other. They can also reason about each other's observation abilities and knowledge derived from these observations. We introduce...
Chapter
This chapter is about the model construction problem in some classes of models: models satisfying the conditions of reflexivity, seriality, symmetry, and combinations thereof. The corresponding logics are KT, KD, KB, KTB, and KDB. We also consider models whose accessibility relation is confluent (logic K.2) or is an equivalence relation (logic KT45...
Chapter
This chapter is about the model construction problem in classes of models satisfying the constraint of transitivity. We present the modal logics of the class of models where the accessibility relation is transitive (K4), transitive and serial (KD4), and transitive and reflexive (KT4, alias S4). For these logics, the model construction procedure may...
Chapter
This chapter is about the basic modal logic K and its multimodal version K n . We also present the basic description logic ALC, which can be viewed as a notational variant of K n . The implementation of reasoning methods for all these logics can be done by means of the most basic rules, that are combined by the most basic strategies: fair strategie...
Chapter
This chapter shows how to implement model checking in LoTREC. There are two reasons why this topic is placed here: first, the implementation of model checking in LoTREC requires us to extend the tagging primitives of Chap. 5; second, model checking is going to be used in the next chapter.
Chapter
This last chapter is about the model construction problem in classes of models having relations that are transitive closures of other relations. The main such logics are linear-time temporal logic LTL and propositional dynamic logic PDL. These logics require both blocking and model checking.
Chapter
We introduce Kripke models. With the help of a series of examples we present the main modal concepts that can be interpreted by means of possible worlds semantics: the concepts of event, action, program, time, belief, knowledge, and obligation. In the end of the chapter we show how Kripke models can be built by means of LoTREC and give a formal def...
Chapter
We introduce a general formal language in order to talk about properties of Kripke models. We then show how such languages can be defined in LoTREC and how to check that a formula is true in a given world of a given Kripke model. The latter is called model checking. Beyond model checking we also introduce the reasoning tasks of satisfiability check...
Book
Possible worlds models were introduced by Saul Kripke in the early 1960s. Basically, a possible world's model is nothing but a graph with labelled nodes and labelled edges. Such graphs provide semantics for various modal logics (alethic, temporal, epistemic and doxastic, dynamic, deontic, description logics) and also turned out useful for other non...
Article
Full-text available
Despite the fact that epistemic connectives are sometimes interpreted in concrete structures defined by means of runs and clock time functions, one of the things that strikes one when studying multiagent logics is how abstract their semantics are. Contrasting this fact is the fact that real agents like robots in everyday life and virtual characters...
Conference Paper
Full-text available
We present a tool (Satoulouse) that can help teachers, particularly in computer science, to convince undergraduate students that logic may be powerful. It is to be used very early in a logic course, in order to enhance students’ motivation to learn propositional logic. Satoulouse simply consists of a friendly interface that offers several syntactic...
Conference Paper
Full-text available
In this paper, we give a logic for perception and knowledge: Flatland. This semantics of this framework is a concrete Kripke model so that it is an easy-to-understand toy example for students. We present a piece of software called Plaza’s world enabling to check formulas in such a concrete Kripke model and to announce formulas.
Conference Paper
Full-text available
We present a proof assistant in Natural Deduction for undergraduate students. The system is interactive: you can combine, delete, modify proofs with a easy-to-use graphical interface. We discuss the pedagogical benefit of this tool.
Conference Paper
Full-text available
In this paper we investigate a concrete epistemic situation: there are agents (humans, robots, cameras, ...) and propositions (lamps on or off, obstacles dangerous or not, ...) located in Lineland. We express properties with the standard epistemic logic language like "Agent A knows that agent B knows that lamp L is on". We give some words about mod...
Conference Paper
Full-text available
Unless one strictly uses standard modal logics, there is a need for a generic tool allowing easy implementation of provers or model builders for most of multi modal logics. This is what LoTREC 1 aims at. It offers a high-level language for describing tableaux calculi specified by means of rules rewriting patterns together with a strategy specifying...
Article
Full-text available
We show that Pauly's Coalition Logic can be embedded into a richer normal modal logic that we call Normal Simulation of Coalition Logic (NCL). We establish that the latter is strictly more expressive than the former by proving that it is NEXPTIME complete in the case of at least two agents.
Conference Paper
In this paper we prove that the satisfiability problem for the class of what we call layered modal logics (LML) is in NEXPTIME, and hence, is decidable. Roughly, LML are logics characterized by semantical properties only stating the existence of possible worlds that are in some sense “further” than the other. Typically, they include various conflue...
Article
Full-text available
This paper, we propose a modal logic satisfying minimal requirements for reasoning about diagrams via collection of sets and relations between them, following Harel's proposal. We first give an axiomatics of such a theory and then provide its Kripke semantics. Then we extend previous works of ours in order to obtain a decision procedure based on ta...
Chapter
This paper addresses the problem of automated deduction for Humberstone's inaccessible worlds logic. We exhibit a sound and complete translation into a normal bimodal logic for which efficient proof methods have been devised in the last years. By the way, our translation provides a sound, complete and finitary axiomatization of Humberstone's inacce...
Article
Abstract In this paper we prove that adding a confluence axiom to a modal logic which behaves rather well from the viewpoint of complexity of the satisfaction problem, drastically increases its complexity and blows it up from PSPACE-completeness to NEXPTIME-completeness. More precisely, we investigate here both monomodal,K + confluence and bimodal...
Conference Paper
Full-text available
In this paper we study formal tools for the definition of tableaux systems for modal logics. We begin by some preliminaries about graphs. Then we present graph rewriting rules together with control constructs for defining strategies of application of these rules. We establish fair strategies that are sound, complete and terminating. These results c...
Article
Full-text available
In this paper we prove that adding a confluence axiom to a modal logic which behaves rather well from the viewpoint of complexity of the satis-faction problem, drastically increases its complexity and blows it up from PSPACE-completeness to NEXPTIME-completeness. More precisely, we investigate here both monomodal K + confluence and bimodal K with c...
Conference Paper
Full-text available
In this paper we describe a generic tableaux system for build- ing models or counter-models and testing satisfiability of formulas in modal and description logics. This system is called LoTREC2.0. It is characterized by a high-level language for tableau rules and strategies. It aims at covering all Kripke-semantic based logics. It is implemented in...
Article
Full-text available
In this paper we present some examples of decision procedures based on tableau calculus for some mono- and multimodal logics having a semantics involving properties that are not easily representable in tree-like structures (like e.g. density, confluence and persistence). We show how to handle them in our framework by generalizing usual tableaux (wh...
Article
If work in psychology has clearly brought to light that 'conceptual flexibility' exists in the categorization of objects, which led to re-questioning the traditional conception of categorization which considers rigid and discontinuous categories, it is not the case in linguistics and psycholinguistics. We propose, through highlighting the role of a...
Conference Paper
Full-text available
If work in psychology has clearly brought to light the existence of "conceptual flexibility" in the categorisation of objects, which led to a re-questioning of the traditional conception of categorisation which considers rigid and discontinuous categories, it is not the case in linguistics and psycholinguistics. We propose, through a highlighting o...
Conference Paper
Full-text available
The last years have seen a renewed interest in modal and description logics (MDLs). Better algorithms, coding, and technology have led to effective systems based on tableau and constraint systems [6 7] to DPLL-based implementations
Conference Paper
In this paper we investigate tableau proof procedures for reasoning about actions and plans. Our framework is a multimodal language close to that of propositional dynamic logic, wherein we solve the frame problem by introducing the notion of dependence as a weak causal connection between actions and atoms. The tableau procedure is sound and complet...
Article
We present the basic framework of a logic of actions and plans defined in terms of modal logic combined with a notion of dependence. The latter is used as a weak causal connection between actions and literals. In this paper we focus on the frame problem and demonstrate how it can be solved in our framework in a simple and monotonic way. We give the...
Article
that the indirect effects of actions should be described by static integrity constraints (and not by actions laws). Then the so-called ramification problem is the problem of deducing new action laws from the given ones plus the static integrity constraints. This is straightforward in LAP: E.g. 2(Loaded ! [shoot]Dead 2(Dead $ :Alive)) implies 2(Load...
Article
this paper we have designed tableau calculi for modal logics which Kripke models have an underlying structure richer than discrete trees and we have clearly separated the study of completeness from that of termination. This permits to obtain more modular proofs.
Article
The problem of completeness for predicate modal logics is still under investigation, although some results have been obtained in the last few years (cf. [2, 3, 4, 7]). As far as we know, the case of multimodal logics has not been addressed at all. In this paper, we study the combination of modal logics in terms of combining their semantics. We demo...
Article
Full-text available
. In this paper we generalize the existing tableau methods for modal logics. First of all, while usual modal tableaux are based on trees, our basic structures are rooted directed acyclic graphs (RDAG). This allows natural tableau rules for some modal logics that are difficult to capture in the usual way (such as those having an accessibility relati...
Article
Full-text available
We investigate modal tableau proof procedures for reasoning about actions and plans. We solve the frame problem by replacing the frame axioms by a dependence relation between actions and literals. We show how a tableau method for the resulting logic can be defined from the basic modal tableaux for modal logics K and S4 in order to take into account...
Article
We extend the monotonic and regular modal logics to the multi-modal cue, and give semantical characterization (soundness and completeness) w.r.t. a semantics of minimal frames. For this we introduce a calculus over neighbourhoods and we obtain simpler conditions than those from the literature (essentially [3]).
Article
Full-text available
. Classical modal logics generally neither possess the necessitation rule nor the K-axiom. Their semantics being in terms of minimal models, several specialisations of these have been given such as augmented minimal models, models with queer worlds or models with inaccessible worlds. In this paper we exhibit exact translations from these families i...
Article
We prove that a natural and simple predicate modal logic with the Barcan formula, namely QBF-KD plus the axiom of density, is not Kripke complete. Although incompleteness results are known in Kripke semantics, most of the methods used can only apply to logics stronger than QBF-S4 as they are based in a translation from intermediate logics. We give...
Article
Automated deduction methods facilitate the usage of modal logic in AI. Beside methods, both based on deduction rules for the object language (Fitting, 1983) (Enjalbert Fariñas del Cerro, 1986), there are translation methods that rely on an embedding of the Kripke semantics into first-order logic. Translation methods may carry an advantage in that t...
Conference Paper
The aims of this paper are twofold: First, we review the automated deduction method for normal multi-modal logics which has shown to be the most general and fruitful, namely translation into first-order theories, and more precisely, the functional translation into equational theories with ordered sorts Second, to show how this method can be extende...
Article
Full-text available
In this paper we investigate a concrete situation of epistemic spatial reasoning: there are agents (humans, cameras,...) which are located on a line, and according to their respective positions and to where agents are looking at, the epistemic situation will vary. Using standard epistemic logic language, we aim at expressing various properties ("Ag...

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