Papers by Marie-laure Mugnier
In the framework of multi-target use of a given ontology, this paper proposes a representation of... more In the framework of multi-target use of a given ontology, this paper proposes a representation of vocabularies based on the identification of elementary vocabularies, which can be equivalently defin ed using specializations of the "kind of" relation. It defines a way of combin- ing contexts and vocabularies that allows context-specific querying.
Principles of Knowledge Representation and Reasoning, 2010
We consider positive rules in which the conclusion may contain existentially quantified variables... more We consider positive rules in which the conclusion may contain existentially quantified variables, which makes reasoning tasks (such as Deduction) undecidable. These rules have the same logical form as TGD (tuple-generating dependencies) in databases and as conceptual graph rules. The aim of this paper is to provide a clearer picture of the frontier between decidability and non-decidability of reasoning with these rules. We show that Deduction remains undecidable with a single rule; then we show that none of the known abstract decidable classes is recognizable. Turning our attention to concrete decidable classes, we provide new classes and classify all known classes by inclusion. Finally, we study, in a systematic way, the question "given two decidable sets of rules, is their union decidable?", and provide an answer for all known decidable cases except one.
Description Logics, 2008
Simple conceptual graphs can be seen as a very basic description logic, allowing however for answ... more Simple conceptual graphs can be seen as a very basic description logic, allowing however for answering conjunctive queries. In the first part of this paper, we translate some results obtained for conceptual graph rules of form "if A then B" into an equivalent DL-based formalism. Then we show that, our algorithms can automatically decide in some cases whether a given DL has the FOL-reducibility property, provided that the semantics of its constructors can be expressed by rules.
International Joint Conference on Artificial Intelligence, 2001
Google, Inc. (search). ...
Journal of Artificial Intelligence Research, 2002
Lecture Notes in Computer Science, 2006
Query containment is a fundamental problem of databases. Given two queries q1 and q2, it asks whe... more Query containment is a fundamental problem of databases. Given two queries q1 and q2, it asks whether the set of answers to q1 is included in the set of answers to q 2 for any database. In this paper, we investigate this problem for conjunctive queries with negated subgoals. We use graph homomorphism as the core notion, which leads us to extend the results presented in [Ull97] and [WL03]. First, we exhibit sufficient (but not necessary) conditions for query containment based on special subgraphs of q2, which generalize that proposed in . As a corollary, we obtain a case where the time complexity of the problem decreases. From a practical viewpoint, these properties can be exploited in algorithms, as shown in the paper. Second, we propose an algorithm based on the exploration of a space of graphs, which improves existing algorithms.
Lecture Notes in Computer Science, 1996
. This paper presents graph operations for processing conceptualgraph rules in forward chaining a... more . This paper presents graph operations for processing conceptualgraph rules in forward chaining and backward chaining. In both casesthe operations provide sound and complete procedures with respect tofirst-order logic deduction. First we present our framework: simple conceptualgraphs, rules as couples of lambda-abstractions, knowledge base,logical semantics. Next we focus on forward chaining. In particular, usingthe notion of redundancy, we exactly characterize
Cet article présente les premières étapes de conception d'un moteur d'inférence pour un outil ind... more Cet article présente les premières étapes de conception d'un moteur d'inférence pour un outil industriel de gestion des connaissances. Le logiciel existant permet la construction et l'exploitation de bases de connaissances comportant un méta-modèle, des ontologies et des instances en s'appuyant sur le langage des Topic Maps. Les Topic Maps ne disposant pas de sémantique formelle mais reposant sur un modèle de graphes étiquetés, nous proposons de nous appuyer sur le formalisme des graphes conceptuels pour la mise en oeuvre de raisonnement sur ces bases. Nous présentons une transformation réversible des Topic Maps vers les graphes conceptuels qui nous permet à la fois de doter le langage des Topic Maps d'une sémantique formelle, d'exploiter les mécanismes de raisonnement des graphes conceptuels et de réutiliser l'API CoGITaNT pour l'implémentation des mécanismes d'inférences.
ACM SIGPLAN Notices, 1992
The main topic of this paper is multiple inheritance and conflict resolution methods in Object Or... more The main topic of this paper is multiple inheritance and conflict resolution methods in Object Oriented Programming.
ACM SIGPLAN Notices, 1994
studies concerning multiple inheritance convinced us that a better analysis of conflict resolutio... more studies concerning multiple inheritance convinced us that a better analysis of conflict resolution mechanisms was necessary. In [DHHM92], we stated properties tPlease send correspondence concerning this paper to M.
Lecture Notes in Computer Science, 1993
This paper studies canonical graphs, which are conceptual graphs derivable from a canonical basis... more This paper studies canonical graphs, which are conceptual graphs derivable from a canonical basis. We provide several characterizations of canonical graphs and prove that the correspondence between notions of a projection and a derivation sequence (specialization) holds true for canonical graphs. We propose an algorithm for deciding whether a conceptual graph is canonical relative to a given canonical basis. The
Lecture Notes in Computer Science, 1993
The main purpose of this paper is to develop polynomial algorithms for the projection and matchin... more The main purpose of this paper is to develop polynomial algorithms for the projection and matching operations on conceptual graphs. Since all interesting problems related to these operations are at least NP-complete — we will consider here the exhibition of a solution and counting the solutions — we propose to explore polynomial cases by restricting the form of the graphs
Lecture Notes in Computer Science, 1993
An analytical study of the Sowa's elementary specialization operations is present... more An analytical study of the Sowa's elementary specialization operations is presented in this paper. Each operation is studied independently, then combined with the others. Some complexity results are proven. For instance, the elementary decision problems, related to these operations, are shown to be isomorphic-complete or NP-complete. The main objective of this paper is a better understanding of the reasons of
Database and Expert Systems Applications, 2010
We consider the containment problem for conjunctive queries with atomic negation. Firstly, we ref... more We consider the containment problem for conjunctive queries with atomic negation. Firstly, we refine an existing algorithm based on homomorphism checks, which itself improves other known algorithms in databases, and analyze it experimentally. Secondly, we present a new algorithm based on the translation of the containment problem into the problem of checking the unsatisfiability of a propositional logical formula, which
Lecture Notes in Computer Science, 2011
We tackle the containment problem for conjunctive queries with negation, which takes two queries ... more We tackle the containment problem for conjunctive queries with negation, which takes two queries q 1 and q 2 as input and asks if q 1 is contained in q 2. A general approach for solving this problem consists of considering all completions of q 1 (intuitively these completions represent all canonical databases that satisfy q 1) and checking if
We consider the entailment problem in the fragment of first-order logic (FOL) composed of existen... more We consider the entailment problem in the fragment of first-order logic (FOL) composed of existentially closed conjunctions of literals (without functions), denoted FOL(∃, ∧, ¬ a ). This problem can be recast as several fundamental problems in artificial intelligence and databases, namely query containment for conjunctive queries with negation, clause entailment for clauses without functions and query answering with incomplete information for Boolean conjunctive queries with negation over a fact base. Entailment in FOL(∃, ∧, ¬ a ) is Π P 2 -complete, whereas it is only NP-complete when the formulas contain no negation. We investigate the role of specific literals in this complexity increase. These literals have the property of being "exchangeable", with this notion taking the structure of the formulas into account. To focus on the structure of formulas, we shall see them as labeled graphs. Graph homomorphism, which provides a sound and complete proof procedure for positive formulas, is at the core of this study. Let ENTAILMENT k be the following family of problems: given two formulas g and h in FOL(∃, ∧, ¬ a ), such that g has at most k pairs of exchangeable literals, is g entailed by h? The main * 1 results are that ENTAILMENT k is NP-complete if k is less or equal to 1, and P N P || -complete for any value of k greater or equal to 3. As a corollary of our proofs, we are able to classify exactly previous problems when g is decomposable into a tree.
Computational Intelligence, 1998
We study the expressiveness of Nested Graphs, an extension of conceptual graphs. Nesting is intro... more We study the expressiveness of Nested Graphs, an extension of conceptual graphs. Nesting is introduced as a formal version of the intuitive "zooming in" on descriptions of individuals. Projections are defined inductively as the formal tool for "reasoning with nested graphs." Nested graphs are translated to "colored" formulas. Coloring represents anaphoras in a way similar to conceptual graphs. A system of Gentzen sequents is shown to be adequate and complete with respect to projections of nested graphs.
International Conference on Conceptual Structures, 2004
This paper tackles the question of representing and reasoning with types and coreference in simpl... more This paper tackles the question of representing and reasoning with types and coreference in simple conceptual graphs (SGs). It presents a framework integrating a number of previous works. This proposal is guided by the usability of CGs in practice. In other words, notions should be easy to use in knowledge representation and operations for doing reasoning have to be efficiently
International Conference on Conceptual Structures, 1997
. This paper deals with positive (i.e. without negation) nestedconceptual graphs (NCGs). We first... more . This paper deals with positive (i.e. without negation) nestedconceptual graphs (NCGs). We first give a general framework - graphs ofgraphs provided with morphism - for defining classes of NCGs. Then wedefine a new class of NCGs - typed NCGs - and we show that known kinds ofNCGs can be described very simply as classes of the general framework. AllNCG
Lecture Notes in Computer Science, 2014
. The main objective of this paper is to add one more brick inbuilding the CG model as a knowledg... more . The main objective of this paper is to add one more brick inbuilding the CG model as a knowledge representation model autonomousfrom logic. The CG model is not only a graphical representation of logic, it ismuch more: it is a declarative model encoding knowledge in a mathematicaltheory, namely labelled graph theory, which has efficient computable forms,with a fundamental graph
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Papers by Marie-laure Mugnier