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C-ACTI; International audience; Performance of transport protocols on lossy links is a well researched topic, however there are only a few proposals which make use of the opportunities presented by the use of erasure coding within the transport layer, particularly in the multipath transport protocol context. In this paper, we investigate the improvements in the performance of multipath SCTP transport protocol brought by the novel integration of the on-the-fly erasure code into the congestion control and reliability mechanisms of CMT-SCTP. Our contributions include: integration of transport protocol and erasure codes with regards to congestion control and reliability mechanisms; proposal for a variable retransmission delay parameter in the sender (aRTX) adjustment; evaluation of the performance of CMT-SCTP with erasure coding with simulations. Our results show that we can achieve from 10% to 80% improvements in application goodput under lossy multipath network conditions without a significant penalty i.e. with a minimal (10%) overhead due to the encoding-decoding process. We further evaluate the performance of video streaming using an equivalent of partially reliable CMT-SCTP with erasure coding and again demonstrate a solid performance improvement for our proposal, compared to CMT-SCTP. Finally, we provide an analytical evaluation of CMT-SCTP with erasure codes and validate this with simulation results.

C-COM; International audience; Lorsque l’on comprend ce qu’est la SOA, quels sont ses avantages et ses inconvénients, la première question qui se pose est : "comment procéder ?". Il n’y a pas de réponse unique. Cependant, il est nécessaire de suivre une méthodologie de conception de simulations ou encore un processus de simulation. Elle consiste à définir la suite d’opérations à réaliser pour obtenir une simulation d’une partie du monde réel. Nous proposons dans cet article un tronc commun aux différentes méthodologies de conception de simulations. Ensuite, nous présentons une nouvelle approche facilitant la co-construction (la collaboration entre des thématiciens pour construire un modèle) et la réutilisation de modèle, tirant parti de DOM et aMVC. Enfin, nous appliquons cette approche méthodologique sur un exemple et proposons quelques perspectives.

C-ACTI; International audience; The multi-agent systems are successfully used in modeling of dynamic complex systems, and simulations of these models reinforce the knowledge of experts and even allow them to explore new horizons or to cross boundaries. This is the reason why the models being tackled are increasingly varied, and as one goes along with experimentations, these models are completed, intercrossed. Consequently they become increasingly complex. In our previous work [1], we proposed a first modeling approach to support this complexity increase: the Dynamic- Oriented Modeling (DOM). The application of this approach can effectively support the increase of the model. This increase applies to both agents and environments. This DOM approach tackles the problem of the latter by splitting in multiple parts. But if DOM led to organize properly the multiple environments that come into play, little support is provided to organize and manage the increasing complexity of the agents themselves... Inevitably, when we reach a quite advanced stage of evolution of the model, the agents eventually reach a critical mass (either in formalization or code) that makes them more and more hard to comprehend. In this paper, we illustrate this phenomenon and show that it quickly takes the upper hand against the benefits of DOM, as it can eventually block the potential development, or even reuse, of the model. Then we explain that a solution to this ”side effect” could structure the architecture of agents, a structure capable of maintaining readability and flexibility of the formalization of the agent throughout the growth process of the global model.We study a well known pattern in software engineering: the MVC pattern, which can be reused here to meet this objective. We will present in details how this pattern could be instantiated in the field of MAS architecture, and how, ultimately, it can be an effective new way to formalize agents in a method called Multi- Behaviors Modelization.

In the last few years, the multiagent system's paradigm has been more and more used in various fields, specially in the simulation field (MAS). Whenever a new application came into being and has been validated by its review board, specialists usually want to reuse it, fully or partially, in order to cut down the time and price of developing similar application. But this reuse is not as simple as expected. In a previous article, we proposed the DOM modeling to tackle modeling difficulties which arise in a complex system. However this solution has its limits as we will develop here. In this paper, we define a more complete agent modeling, based on the MVC design pattern, in order to to push back these limits.

National audience; no abstract

International audience; Green sea turtles (Chelonia mydas) inhabit tropical and subtropical oceans worldwide. Living in the marine environment and laying eggs on the beach, they are mainly threatened by human activities (poaching, fisheries bycatch, habitat destruction, etc.). In Reunion Island, the Kélonia observatory and IFREMER develop various scientific programs to study and protect sea turtles. One of them consists in studying migrations of green sea turtles for mating purpose. As existing mathematical models struggle to take spatial dimension into account, we propose an agent-based model to study some of the numerous questions regarding green sea turtles migrations. Coming with high expectations, experts in sea turtles also provide many heterogeneous but incomplete data. Considering available or obtainable data in one hand and the various questions of experts in the other hand, we defined an innovative modelling process in which we simultaneously conduct discussion with experts and prototyping. This paper aims at presenting our simulation model but also our approach as well as the data-collection and modelling roadmap it produced.

National audience; no abstract

National audience; no abstract

National audience; Un projet nommé GERRI a été lancé à la Réunion dans le but de favoriser le développement de nouvelles technologies écologiques. Une des pierres fondamentales de ce projet est la maitrise de l'énergie, dont l'aménagement énergétique d'un territoire fait partie. Les recherches dans ce dernier domaine du projet sont peu foisonnantes. Nous proposons dans cet article une nouvelle approche qui passera par la modélisation de l'aménagement énergétique du territoire, grâce aux systèmes multi-agents. Nous exploiterons plus particulièrement la possibilité de géo-localiser les agents, afin d'obtenir des avantages non accessible dans les autres approches qui, pour la plupart, ne prennent pas la localisation en considération. La localisation géographique apporte une nouvelle dimension, car il est possible de visualiser les flux d'énergies et donc d'optimiser les pertes dues aux transports. Il est aussi possible grâce à cet outil de simulation d'argumenter certains choix au niveau production d'énergie, ou encore de discuter de certaines politiques de consommation.

International audience; In an earlier work, a termination analyzer for Java bytecode was developed that translates a Java bytecode program into a constraint logic program and then proves the termination of the latter. An efficiency bottleneck of the termination analyzer is the construction of a proof of termination for the generated constraint logic program, which is often very large in size. In this paper, a set of program simplifications are presented that reduce the size of the constraint logic program without changing its termination behavior. These simplifications remove program clauses and/or predicate arguments that do not affect the termination behavior of the constraint logic program. Their effect is to reduce significantly the time needed to build the termination proof for the constraint logic program, as our experiments show.

International audience; no abstract

Our questioning emerges from the establishment of a new teaching, called Scientific Methods and Practices (MPS), as part of the French high school reform in 2010. This multidisciplinary teaching, which aims to initiate pupils to a scientific approach, leds mathematics teachers to question and to change their practices. We propose to analyze these changes in terms of resources and the way teachers work on these resources. We retain two approaches: the double approach didactic and ergonomic of the teaching practices (Robert, 2010a; Rogalski, 2010) and the documentational approach of didactics (Gueudet et Trouche, 2010). Our research is conducted from observations of mathematics teachers involved in MPS and engaged in different disciplinary and multidisciplinary collectives. These observations are supplemented by interviews with colleagues in other disciplines. We also performed a study of resources available for one of the themes proposed. This study is part of the research program ReVEA (Living Resources for Teaching and Learning), supported by the ANR. Our thesis aims to show the impact of resources and lack of resources from understanding the prescribed task to the effective task, and also the impact of the different collectives in which the mathematics teacher is involved. It questions as well the effects of this work on professional development, especially regarding the inquiry-based science teaching., Notre questionnement trouve sa source dans la mise en place, dans le cadre de la réforme du lycée de 2010, de l'enseignement d'exploration Méthodes et Pratiques Scientifiques (MPS) en Seconde. Cet enseignement pluridisciplinaire, visant à initier les élèves à la démarche scientifique dans le cadre d'un projet, a conduit les enseignants de mathématiques, à interroger et à modifier leurs pratiques. Nous proposons d'analyser ces changements sous l'angle des ressources et du travail des enseignants sur ces ressources. Nous mobilisons les cadres théoriques de la double approche didactique et ergonomique (Robert, 2010a ; Rogalski, 2010) et de l'approche documentaire du didactique (Gueudet et Trouche, 2010). Notre recherche est conduite à partir du suivi de professeurs de mathématiques impliqués en MPS et engagés dans différents collectifs disciplinaires et pluridisciplinaires. Ce suivi est complété par des entretiens avec les collègues des autres disciplines. Nous avons aussi effectué une étude sur l'offre des ressources disponibles pour l'un des thèmes proposés. Cette étude s'inscrit dans le programme de recherche ReVEA (Ressources Vivantes pour l'Enseignement et l'Apprentissage), soutenu par l'ANR. Notre thèse propose de montrer l'impact des ressources et de leur manque depuis la compréhension de la tâche prescrite jusqu'à la tâche effective, ainsi que celui des différents collectifs dans lesquels le professeur de mathématiques est impliqué. Elle questionne également les effets de ce travail sur le développement professionnel concernant en particulier la conception et la mise en œuvre de séances fondées sur des démarches d'investigation.

We present a type system for linear constraints over the reals intended for reasoning about the input-output directionality of variables. Types model the properties of definiteness, range width or approximation, lower and upper bounds of variables in a linear constraint. Several proof procedures are presented for inferring the type of a variable and for checking validity of type assertions. We rely on theory and tools for linear programming problems, linear algebra, parameterized polyhedra and negative constraints. An application of the type system is proposed in the context of the static analysis of constraint logic programs. Type assertions are at the basis of the extension of well-moding from pure logic programming. The proof procedures (both for type assertion validity and for well-moding) are implemented and their computational complexity is discussed. We report experimental results demonstrating the efficiency in practice of the proposed approach.

Stability during the biped locomotion and especially humanoid robots walking is a big challenge in robotics modelling. This paper compares the classical and novel methodologies of modelling and algorithmic implementation of the impact/contact dynamics that occurs during a biped motion. Thus, after establishing the free biped locomotion system model, a formulation using variational inequalities theory via a Linear Complementarity Problem then an impedance model are explicitly developed. Results of the numerical simulations are compared to the experimental measurements then the both approaches are discussed.

Over the last decade, many researchers have focused on the study of different urban hierarchies and their evolution over time. These studies may or may not confirm Zipf’s law and emphasize the characteristics of urban growth. The question is then whether urban growth depends upon city-size or not, which is a main issue in modern regional economics. Using data on Chinese cities for the period 1960-2000, this paper aims to provide some answers to this question which has led to a recent passionate debate between the random growth theories and the endogenous growth theories., Durant ces dernières années,un ensemble de travaux originaux ont été consacrés à l'étude des hiérarchies urbaines et à l'organisation en réseau des villes. A l'issue de ces travaux, confirmant ou infirmant la validité de la loi de Zipf, certains chercheurs ont montré qu'il était nécessaire d'intégrer une approche dynamique visant à étudier la croissance, absolue et relative, des villes, afin de comprendre les changements de leurs positions au sein même d'un système urbain donné. Ces travaux débouchent sur une interrogation quant à la nature de la croissance urbaine, "aléatoire" ou "endogène",et la relation fondamentale entre la taille d'une ville et sa croissance. En s'appuyant sur l'étude de l'évolution du système urbain chinois entre 1984 et 2004, cet article apporte une contribution au débat qui oppose les approches de la croissance urbaine aléatoire à celles de la croissance urbaine endogène.

In this paper, using the Brouwer topological degree, the authors prove an existence result for finite variational inequalities. This approach is also used to obtain the existence of periodic solutions for a class of evolution variational inequalities.

Simulation modelling of complex systems nowadays is an ideal solution to get a good understanding of these systems. In effect, compared with real experiments in the field of studies considered, virtual experiments allow one to quickly answer questions about these systems and provide solutions within a delay well adapted to their actual context. This thesis deals with the issue of human action representation, accounting with its temporal and spatial dimensions at individual and collective levels. This question has already been addressed in the field of Artificial intelligence in general and in the one of Agricultural systems in particular, the latter being the application domain of this thesis. The models proposed to date were mainly based upon the theory of planned action, explicitly accounting with the temporal dimension of action only. The main limits of these models lie in their complexity, because the ability to predict all future changes in actors' behaviors is far too difficult. This difficulty leads to the need of frequently re-planning the course of actions in order to get consistent results. The second drawback lies in the discrepancy that may arise between the results of simulated actions and actual observations. In effect, real actors do not realize systematically the actions they forecast according to the situations they actually encounter. In order to overcome the limits of planning models, we developed a model of human action based on the theory of situated action. Action is there viewed as a process endowed with a temporal thickness and emerging from the situations created by the interaction, through time and space, between the actor and its environment. Our model combines the concepts of affordance and stigmergy as well as the notion of emergence. Therefore we propose a multi-agents system within which space is explicitly represented and partitioned into a set of “places”. The control of each place is left to an abstract agent standing for an observer capable of detecting the affordances occurring on its place and trigger appropriate actions. Actors as well as passive objects are represented as “environmental entities”. These entities carry information about their capacity of performing or undergoing actions. This information allows the agents to detect affordances thanks to the meta-knowledge they hold. Once detected, these affordances are reified in the environment to be used to determine the action that will eventually be executed. Coordination of actions, at the collective level, is performed through stigmergy: the agents communicate implicitly between them using a set of marks as a metaphor of pheromons in ant colonies. To prove the relevance of the proposed model, a software prototype, applied to the domain of agricultural production systems, has been implemented with the simulation platform AnyLogic., La modélisation et la simulation des systèmes complexes constitue une solution idéal pour comprendre ces systèmes. En effet, l'expérimentation virtuelle permet, par rapport à l'expérimentation réelle dans le champ d'étude considéré, d'apporter des réponses plus rapides aux questions posées sur ces systèmes, ce qui donne la possibilité de proposer des solutions en un temps adapté au contexte réel. Ce travail traite la question de la représentation de l'action humaine en prenant en compte sa dimension temporelle et spatiale aux échelles individuelle et collective. Cette question a déjà été traitée dans le domaine de l'intelligence artificielle, en général, et celui des systèmes agricoles, en particulier, qui constitue le domaine d'application de cette thèse. Les modèles proposés jusqu'à présent se basaient principalement sur la théorie de l'action planifiée en ne prenant en compte que la dimension temporelle de l'action. Les limites majeures de ces modèles résident dans leur complexité dans la mesure où il est difficile de pouvoir prédire l'ensemble des changements futurs dans l'environnement de l'acteur. Cela conduit à la nécessité de re-planifier fréquemment les actions afin d'obtenir des résultats cohérents. La deuxième limite réside dans l'écart qu'il peut y avoir entre les résultats des actions simulées et la réalité observée. En effet, un acteur ne réalise pas systématiquement les actions qu'il prévoit selon les situations réelles dans lesquelles il se trouve. Afin de pallier aux limites des modèles de l'action planifiée, nous avons développé un modèle de l'action humaine qui se base sur la théorie de l'action située. L'action est vue comme un processus doté d'une épaisseur temporelle émergent des situations créées par l'interaction entre l'acteur et son environnement dans le temps et dans l'espace. Notre modèle combine le concept d'affordance, le concept de stigmergie ainsi que la notion d'émergence. Nous proposons donc un système multi-agents dans lequel l'espace est explicitement représenté et partitionné en un ensemble de places. Le pilotage de chaque place est attribué à un agent abstrait. Celui-ci représente un observateur capable de détecter à tout instant les affordances émergentes sur sa place ainsi que de déclencher l'action appropriée. Les acteurs sont représentés comme des entités de l'environnement au même titre que les objets passifs. Ces entités de l'environnement portent un ensemble d'informations sur leurs capacités à exécuter ou subir des actions. Ces informations permettent aux agents, grâce aux méta-connaissances qu'ils détiennent de détecter les affordances. Celles-ci, une fois détectées, sont réifiées dans l'environnement et utilisées par les agents grâce à un mécanisme de sélection d'actions pour déterminer l'action qui sera finalement exécuter. La coordination des actions au niveau collectif se fait par stigmergie : les agents communiquent de façon implicite en utilisant un ensemble de marques qui sont une métaphore des phéromones des colonies de fourmis. Afin de montrer la pertinence du modèle proposé, un prototype appliqué au domaine des systèmes de production agricoles a été implémenté en utilisant la plateforme AnyLogic.

International audience; This article deals with the analysis of the contact complementarity problem for Lagrangian systems subjected to unilateral constraints, and with a singular mass matrix and redundant constraints. Previous results by the authors on existence and uniqueness of solutions of some classes of variational inequalities are used to characterize the well-posedness of the contact problem. Criteria involving conditions on the tangent cone and the constraints gradient are given. It is shown that the proposed criteria easily extend to the case where the system is also subjected to a set of bilateral holonomic constraints, in addition to the unilateral ones. In the second part, it is shown how basic convex analysis may be used to show the equivalence between the Lagrangian and the Hamiltonian formalisms when the mass matrix is singular.

International audience; Emergent phenomena are often relevant for users and developers of simulation models. But the potential reification of these phenomena raises many questions, conceptually (should they be reified?) and technically (how to do it?). In this paper, we show that such a reification can be considered as an effective way to refine simulation models in which direct modifications, that are made laborious by the multiplicity of the entities and behaviors, often leads to the destabilization of the entire system. We propose a reification technique of the emergent phenomena that do emerge in an agent-based simulation. We illustrate this proposition through the reification of new urban areas, an emergent phenomenon observed in a model that we created to simulate land-use evolutions in Reunion Island.

International audience; A LaSalle's Invariance Theory for a class of first-order evolution variational inequalities is developed. Using this approach, stability and asymptotic properties of important classes of second-order dynamic systems are studied. The theoretical results of the paper are supported by examples in nonsmooth Mechanics and some numerical simulations.; Dans cet article, la théorie d'invariance de LaSalle est généralisée pour une classe d'inéquations variationnelles d'évolution du premier ordre. Des résultats de stabilité (au sens de Lyapunov) et d'attractivité sont ensuite obtenus pour des systèmes dynamiques du second ordre non réguliers. Une extension du théorème de Lagrange aux systèmes conservatifs non réguliers est également proposée. Enfin, quelques exemples et simulations numériques illustrent les principaux résultats théoriques.

International audience; In the 21st century, with the advent of ultra high-speed broadband networks (1Gb per second), the Internet will offer new opportunities for innovators to design qualitative services and applications. Indeed, the challenge of such e-services is not only on the technological aspects of Internet with new infrastructures and architectures to conceive. The reality is also on its human and multimedia content delivery, with innovative philosophies of communication to apply in this digital and virtual age. In the context of Teaching and Learning as a human-centered design approach, we propose a new paradigm for thinking the Web, called the Web of Signs, rather than the Web of things. It focuses on the process of making knowledge by sharing signs and significations (Semiotic Web), more than on knowledge transmission with intelligent object representations (Semantic Web). Sign management is the shift of paradigm for education with ICT (e-Education) that we have investigated in such domains as enhancing natural and cultural heritage. In this paper, we will present this concept and illustrate it with two examples issued from La Reunion Island projects in instrumental e-Learning (@-MUSE) and biodiversity informatics (IKBS). This Sign management method was experimented in the frame of our Living Lab in Teaching and Learning at University of Reunion Island.

International audience; Cluster analysis and seriation are basic data mining techniques. We consider here clustering structures that enable us to achieve both a clustering and a seriation, namely the hierarchical, pyramidal, and prepyramidal clustering structures. Cluster collections of these types determine seriations of any data set by providing compatible orders, i.e., total rankings of the whole data set for which the objects within each cluster are consecutive. Moreover, the dissimilarity measures induced from such cluster collections are Robinsonian; in other words, the more distant the objects in a compatible order, the higher the induced dissimilarity value. It results in a one-to-one correspondence between weakly indexed pyramids and the class of Robinsonian dissimilarities, which holds still in a general setting where undistinguishable objects can be detected, and, as shown in this paper, extends, to prepyramids, which are not required to contain arbitrary intersections of clusters.

7 pages; International audience; We consider cluster structures in a general setting where they do not necessarily contain all singletons of the ground set. Then we provide a direct proof of the bijection between semi-proper robinsonian dissimilarities and indexed pre-pyramids. This result generalizes its analogue proven by Batbedat in the particular case of definite cluster structures. Moreover, the proposed proof shows that the clusters of the indexed pre-pyramid corresponding to a semi-proper robinsonian dissimilarity are particular 2-balls of the considered dissimilarity.

Program termination is a hot research topic in program analysis. The last a few years have witnessed the development of termination analyzers for programming languages such as C and Java with remarkable precision and performance. These systems are largely based on techniques and tools coming from the field of constraint programming. In this paper, we first recall an algorithm based on Farkas' Lemma for discovering linear ranking functions proving termination of a certain class of loops. Then we propose an extension of this method for showing the existence of eventual linear ranking functions, i.e., linear functions that become ranking functions after a finite unrolling of the loop. We show correctness and completeness of this polynomial algorithm., La terminaison des programmes est un sujet actif de recherche en informatique. Ces dernières années ont vu l'apparition d'analyseurs de terminaison performants pour des langages comme C ou Java où l'emploi des techniques et outils de la programmation par contraintes est omniprésent. Dans cet article, nous rappelons un algorithme particulier basé sur l'emploi du lemme de Far-kas pour le calcul de fonctions de rang linéaires garantissant la terminaison d'une certaine classe de boucles. Puis nous présentons une extension de cette méthode pour la découverte de fonctions linéaires qui deviennent des fonctions de rang linéaire à terme, c'est-à-dire après un certain nombre de passages dans la boucle. Nous montrons la correction et la complétude d'un algorithme polynomial pour ce problème.

C-INV; International audience; Natural and social systems are the subject of many studies aimed at understanding their characteristic dynamics and functioning. These systems are characterized by a great variety of interaction between their components and by the fact that often, at different levels, collective phenomena give rise to emergent properties. Simulation, that creates an abstraction of a system as it evolve through time, is a particularly appropriate methodology for studying systems that are inaccessible through direct observation and measurement, either because they cannot be reproduced or because they cannot be directly experimented with. Since such systems may be conceptually described in terms of interacting entities endowed with a certain autonomy in a spatial environment, Multi-agent systems simulation have come to the fore in recent times as a relevant modelling approach. I propose to present and discuss lessons learned through several projects modelling projects performed in Reunion Island, a French overseas territory of 2512 square kilometres in the Western Indian Ocean which lead a project on a global scale to achieve energy self-sufficiency by 2030. The Island is perfectly suited to conduct simulation experiments: it is a small multi-ethnic territory with a fast growing population and many geographic constraints, but also many opportunities in sustainable development and requires that any decision should be based on a spatially explicit understanding of complex ecological systems and their interactions with social systems. Two applications in particular will be discussed, one dedicated to the collective management of agricultural biomass and a second to the management on land-use planning driven by the population dynamics and its distribution in the territory.

International audience; Ce papier présente un modèle de représentation de l'action située dans les systèmes agricoles. L'idée est de considérer un système multi-agents dans lequel l'environnement constitue l'entité intelligente qui décide à un instant et dans une localisation donnés de l'action à réaliser. Pour cela nous utilisons le concept d'affordance, de stigmergie et l'approche multi-agents.

International audience; This paper presents a model to represent situated action in farming systems. The idea is to consider a multi-agents system in which the environment is an intelligent entity that has the ability to decide at a given time and space the actions to perform. Surrogates of real actors, called actuators, just execute the action dictated by the agents embedded in the environment. For this, the model is based on the affordance and stigmergy concepts as well as a multi-agents approach.

International audience; L’Informatique est une science vaste qu’il est plus aisé d’étudier sous la forme de domaines fondamentaux. Parmi ces derniers, on peut distinguer le domaine applicatif qui se focalise sur l’aspect logiciel et qui servira de sujet d’étude dans le cadre de la présente communication sur la notion de « transgression ». En effet, le concept de transgression peut revêtir des aspects différents pour une application, en fonction de l'étape considérée de sa réalisation. Chacune de ces étapes est corrélée à un niveau d'abstraction plus ou moins élevé, allant d'une implication matérielle incontournable, jusqu'à une focalisation axée sur l'humain au travers d'une interface graphique mettant en oeuvre des processus d'interaction homme-machine spécifiques. Notre analyse de la transgression sur le domaine de l'application informatique sera décomposée selon les principales étapes suivies depuis la réalisation du logiciel jusqu'à son utilisation.

C-ACTI; International audience; no abstract

The classical technique for proving termination of a generic sequential computer program involves the synthesis of a ranking function for each loop of the program. Linear ranking functions are particularly interesting because many terminating loops admit one and algorithms exist to automatically synthesize it. In this paper we present two such algorithms: one based on work dated 1991 by Sohn and Van Gelder; the other, due to Podelski and Rybalchenko, dated 2004. Remarkably, while the two algorithms will synthesize a linear ranking function under exactly the same set of conditions, the former is mostly unknown to the community of termination analysis and its general applicability has never been put forward before the present paper. In this paper we thoroughly justify both algorithms, we prove their correctness, we compare their worst-case complexity and experimentally evaluate their efficiency, and we present an open-source implementation of them that will make it very easy to include termination-analysis capabilities in automatic program verifiers.

International audience; no abstract

International audience; Using tools from set-valued and variational analysis, we propose a mathematical formulation for a power DC-DC Buck converter. We prove the existence of trajectories for the model. A stability and asymptotic stability results are established. The theoretical results are supported by some numerical simulations with a discussion about explicit and implicit schemes.

International audience; Context: Android is a programming language based on Java and an operating system for embedded and mobile devices, whose upper layers are written in the Android language itself. As a language, it features an extended eventbased library and dynamic inflation of graphical views from declarative XML layout files. A static analyzer for Android programs must consider such features, for correctness and precision. Objective: Our goal is to extend the Julia static analyzer, based on abstract interpretation, to perform formally correct analyses of Android programs. This article is an in-depth description of such an extension, of the difficulties that we faced and of the results that we obtained. Method: We have extended the class analysis of the Julia analyzer, which lies at the heart of many other analyses, by considering some Android key specific features such as the potential existence of many entry points to a program and the inflation of graphical views from XML through reflection. We also have significantly improved the precision of the nullness analysis on Android programs. Results: We have analyzed with Julia most of the Android sample applications by Google and a few larger open-source programs. We have applied tens of static analyses, including classcast, dead code, nullness and termination analysis. Julia has found, automatically, bugs, flaws and inefficiencies both in the Google samples and in the open-source applications. Conclusion: Julia is the first sound static analyzer for Android programs, based on a formal basis such as abstract interpretation. Our results show that it can analyze real thirdparty Android applications, without any user annotation of the code, yielding formally correct results in at most 7 minutes and on standard hardware. Hence it is ready for a first industrial use

International audience; no abstract

International audience; The recent progress in Information and Communication Technologies gave birth to advanced applications in the field of instrumental e-learning. However, most of these applications only propose a limited number of lessons on predetermined pieces, according to the vision of a single music expert. Thus, this article introduces a web platform to create music lessons dynamically and collaboratively, with the assistance of a semi-automatic score annotation module: @-MUSE. To do so, we first describe a new methodology to design such a platform: Sign Management. Then, we detail its general architecture as an Iterative Sign Base System based on a common practice in music learning: score annotation. Lastly, we give various algorithms to generate relevant annotations (explanations) on a score, based on the analysis of musical patterns difficulty.

International audience; This paper proposes a model to represent and simulate human activities in farming systems. Our definition of the activity concept (otherwise said ‘action’) stems from the ‘situated action’ theory (Suchman, 1987). Action may be summarized simply as ‘what people are actually doing’. Therefore, we characterize action according to four dimensions: actors (persons or machines engaged in activity), time (start date, end date and duration), space (locations where action occurs) and the interaction with the actor’s environment. To take into account all these dimensions our model is based on: (i) an ‘agent’ approach, (ii) a mathematical formalism to represent action over time (Guerrin, 2009) and (iii) a discrete representation of space inspired from cellular automata. Our aim is to apply this model to representing the human component of agricultural systems, i.e. the farming practices. Space is modelled as a regular grid, each cell being controlled by a specific autonomous abstract ‘agent’, in the sense of multiagent systems (MAS), called ‘cell-agent’. Since activity depends, according to the situated action paradigm, on its context of occurrence and continuously involves interactions with the environment, we focused on the concepts of stigmergy and affordance to carry the information necessary to realize actions and on a reactive agent approach. The radical notion of reactive agent postulates that agents’ actions are reac-tions to stimuli. Various constraints to be dealt with are imposed by our application domain (farming sys-tems), namely temporal constraints the cell-agents must consider for acting. Consequently, our model, alt-hough mainly based on a stimulus-response mechanism, involves also a process, kept as simple as possible, allowing spatially situated agents to select the most appropriate action when several actions are concurrently possible. For this, priority levels coupled with the stigmergy and affordance concepts are used. Cell-agent actions are realized through specific objects called ‘actuators’ representing, unconventionally, the real actors (e.g. a farmer possibly using equipments, animals, etc.). An actuator is a non-autonomous entity that receives from the cell-agent where it is located the command of actions it must execute. A cell-agent can perceive, at any time, what happens in its neighbouring cells and which are the objects these cells host. In case a cell-agent needs a resource not located in a nearby cell, it can possibly get it by propagating its request through its neighbours. Action is represented by a binary function of time (Guerrin, 2009) and implemented by these ‘actuators’, exhibiting dynamic behaviours, although they are actually directed by the cell-agents they rely on. Action starts and ends according to events detected on processes observed by the cell-agents in their local environ-ment, provided they can access the necessary resources, among which actuators endowed with relevant abili-ties. The course of action is subject to a set of conditions that must remain satisfied for the action goes to its end. In the meanwhile, it may be interrupted, resumed or cancelled. The originality of this work lies in that real ‘actors’ (like persons, animals, machines, etc.) are represented as non-autonomous ‘objects’ and not as autonomous ‘agents’, as it is generally the case in other modelling efforts (e.g., Sierhuis et al., 2006). These objects cannot act by themselves. They just follow the instructions given by the cell-agents they rely upon. Our model allows so one to represent the behaviour of real ‘situated’ actors as if it were the environment that dictated them what to do. Doing this way complies with the situated action theory.

International audience; In this paper, we present a new and alternative mathematical modelling and analysis methodology for a class of non-regular electronic circuits through a rectifier-stabilizer circuit using the superpotentiel of Moreau and the theory of variational inequalities. This methodology is suitable for engineers to study a large class of applications.

International audience; We study the evolution of a class of quasistatic problems, which describe frictional contact between a body and a foundation. The constitutive law of the materials is elastic, or visco-elastic: with short or long memory, and the contact is modelled by a general subdifferential condition on the velocity. We derive weak formulations for the models and establish existence and uniqueness results. The proofs are based on evolution variational inequalities, in the framework of monotone operators and fixed point methods. We show the approach of the viscoelastic solutions to the corresponding elastic solutions, when the viscosity tends to zero. Finally we also study the approach to short memory visco-elasticity when the long memory relaxation coefficients vanish.

International audience; The main object of this paper is to present a general mathematical theory applicable to the study of a large class of linear variational inequalities arising in electronics. Our approach uses recession tools so as to define a new class of problems that we call "semi-complementarity problems". Then we show that the study of semi-complementarity problems can be used to prove new qualitative results applicable to the study of linear variational inequalities of the second kind

Reunion Island will be hosting in the coming years an increasingly important population. Documents dedicated to land-use planning should take this into account to better manage the evolutions of the island. In the context of multidisciplinary research, the challenge of our work is to propose methods and tools to facilitate interactions between computer scientists and thematicians who bring their expertise to the construction of simulation models dedicated to territorial prospective. We co-constructed DS, an agent-based model that simulates the evolutions of the population and of the land-use on the island, and then we focused on the study of emergence, a concept that appears in our simulations in spatial environment. We defined it as a meta-knowledge; and that enabled us to propose a modelling methodology and a formal framework that lead to the introduction of emerging structures in the Agent-Based Simulation platform GEAMAS-NG. The systems, or the entities of the models themselves, can now be aware of the emergence of phenomena and can materialize these phenomena by using the knowledge of thematicians. We finally demonstrated the usefulness of these proposals by experimenting the reification of an emergent phenomenon observed in DS.; L'île de La Réunion, inscrite au patrimoine mondial de l'UNESCO pour la beauté de ses paysages et pour sa biodiversité exceptionnelle, va accueillir dans les prochaines années une population de plus en plus importante. Les documents de planification réglementant l'évolution de l'urbanisation dans l'île doivent donc en tenir compte afin de gérer au mieux l'évolution et la structuration du foncier local. Dans un contexte de recherche pluridisciplinaire, l'enjeu de nos travaux est donc de proposer des méthodes et outils facilitant les interactions entre les informaticiens et les thématiciens qui apportent leur expertise à la construction de modèles de simulation dédiés à la prospective territoriale et de faire en sorte que ces modèles puissent fournir des pistes de réflexions aux décideurs confrontés aux choix de demain afin d'aider à mettre en place une organisation des territoires qui soit la plus cohérente possible. Après avoir participé à la réalisation de DS, un modèle qui permet de simuler conjointement l'évolution de la population et celle du Mode d'Occupation des Sols à La Réunion, nous nous sommes focalisés sur l'étude de l'émergence, une notion qui apparaît dans nos simulations en environnement spatialisé, mais pour laquelle il n'existe pas d'outils génériques permettant de la manipuler. Nous l'avons définie comme étant une méta-connaissance, ce qui nous a permis de proposer une méthodologie de conception de simulations et un cadre formel qui ont abouti à la mise en place de structures émergentes dans la plateforme de simulation GEAMAS-NG. Celle-ci, ou les entités de la SOA elles-mêmes, peuvent ainsi prendre conscience de l'émergence de phénomènes et les matérialiser en ayant recours à la connaissance des thématiciens. Nous avons alors montré l'intérêt de ces propositions en expérimentant la réification de phénomènes émergents observés dans DS.

Reunion Island will be hosting in the coming years an increasingly important population. Documents dedicated to land-use planning should take this into account to better manage the evolutions of the island. In the context of multidisciplinary research, the challenge of our work is to propose methods and tools to facilitate interactions between computer scientists and thematicians who bring their expertise to the construction of simulation models dedicated to territorial prospective. We co-constructed DS, an agent-based model that simulates the evolutions of the population and of the land-use on the island, and then we focused on the study of emergence, a concept that appears in our simulations in spatial environment. We defined it as a meta-knowledge; and that enabled us to propose a modelling methodology and a formal framework that lead to the introduction of emerging structures in the Agent-Based Simulation platform GEAMAS-NG. The systems, or the entities of the models themselves, can now be aware of the emergence of phenomena and can materialize these phenomena by using the knowledge of thematicians. We finally demonstrated the usefulness of these proposals by experimenting the reification of an emergent phenomenon observed in DS.; L'île de La Réunion, inscrite au patrimoine mondial de l'UNESCO pour la beauté de ses paysages et pour sa biodiversité exceptionnelle, va accueillir dans les prochaines années une population de plus en plus importante. Les documents de planification réglementant l'évolution de l'urbanisation dans l'île doivent donc en tenir compte afin de gérer au mieux l'évolution et la structuration du foncier local. Dans un contexte de recherche pluridisciplinaire, l'enjeu de nos travaux est donc de proposer des méthodes et outils facilitant les interactions entre les informaticiens et les thématiciens qui apportent leur expertise à la construction de modèles de simulation dédiés à la prospective territoriale et de faire en sorte que ces modèles puissent fournir des pistes de réflexions aux décideurs confrontés aux choix de demain afin d'aider à mettre en place une organisation des territoires qui soit la plus cohérente possible. Après avoir participé à la réalisation de DS, un modèle qui permet de simuler conjointement l'évolution de la population et celle du Mode d'Occupation des Sols à La Réunion, nous nous sommes focalisés sur l'étude de l'émergence, une notion qui apparaît dans nos simulations en environnement spatialisé, mais pour laquelle il n'existe pas d'outils génériques permettant de la manipuler. Nous l'avons définie comme étant une méta-connaissance, ce qui nous a permis de proposer une méthodologie de conception de simulations et un cadre formel qui ont abouti à la mise en place de structures émergentes dans la plateforme de simulation GEAMAS-NG. Celle-ci, ou les entités de la SOA elles-mêmes, peuvent ainsi prendre conscience de l'émergence de phénomènes et les matérialiser en ayant recours à la connaissance des thématiciens. Nous avons alors montré l'intérêt de ces propositions en expérimentant la réification de phénomènes émergents observés dans DS.

International audience; Coordination is defined as the management of dependencies between activities in order to reach an objective. These dependencies generally concern resource sharing and the compliance with temporal (simultaneity, precedence) and spatial constraints. This management is made according to two principal modes: explicit and implicit. The explicit mode is based on using ‘protocols’ (e.g. procedures, plans) explicitly describing how the agents must perform their actions to guarantee the good functioning of the system they are committed to. The implicit mode, characterized by the absence of protocol, is mainly based on using artefacts, implicitly fostering the behaviour of the agents through their interaction with their physical environment (concepts of ‘stigmergy’ and ‘affordance’). In this paper we try to synthesize theories and relevant concepts necessary to represent coordination. Our goal is to propose, at last, a modelling framework to simulate the coordination of human activities in complex agricultural production systems.

Performance analysis is a common issue in the musical field, especially for instrument teachers and musicologists. That is why we present in this paper an ontology (technical aspect) and a descriptive model (pragmatic aspect) to allow music teachers and students to create semantic annotation on musical performances. As such, we start by studying recorded piano lessons and analyze the required concepts and roles. We then propose a general performance description model based on these lessons and detail how musicology rules can be used to automatically infer new information on a given piece. Lastly, we discuss the integration of our work to an e-learning web-based collaborative platform for musical education.

International audience; In the field of E-learning, the goal of researchers in knowledge acquisition and transmission is to produce e-services that are genuinely useful, that is to say, perfectly adapted to their end-uses. Here, we will deal with the specificities of learning how to play a musical instrument for which the quality of learning depends on the quality of teaching methods. In this context, semantic management of tacit and explicit knowledge from experts and books is not enough. Knowledge engineers must also capture live interpretations of expert musicians to illustrate the lesson to be learned. To enhance these significations, Sign management is a concept that has more relevance than Knowledge management: it aims at indexing multimedia contents (i.e. annotations) on different on/off-line supports with formalized textual information (i.e. scores) in order to better share interpretations and viewpoints. In this paper, we explain our concept of Sign management in the new digital and relational ecosystem. We then describe an iterative method based on a Creativity Platform that establishes end-uses as the criterion by which e-services are developed. The Creativity Platform serves to better understand the transformation of a given tool (proposed offer) into an instrument (motivated demand), which, in turn, motivates the supply that is produced to meet the demand. We illustrate our method based on activity theory by using an example of instrumental e-learning, the e-guitar project. Finally, we discuss the pragmatic results of our co-design experience with end-users.

We introduce an extension of linear constraints, called linear- range constraints, which allows for (meta-)reasoning about the approximation width of variables. Semantics for linear- range constraints is provided in terms of parameterized linear systems. We devise procedures for checking satisfiability and for entailing the maximal width of a variable. An extension of the constraint logic programming language CLP(R) is proposed by admitting linear-range constraints.

International audience; It is important to prove that supposedly terminating programs actually terminate, particularly if those programs must be run on critical systems or downloaded into a client such as a mobile phone. Although termination of computer programs is generally undecidable, it is possible and useful to prove termination of a large, non-trivial subset of the terminating programs. In this paper we present our termination analyser for sequential Java bytecode, based on a program property called path-length. We describe the analyses which are needed before the path-length can be computed, such as sharing, cyclicity and aliasing. Then we formally define the path-length analysis and prove it correct w.r.t. a reference denotational semantics of the bytecode. We show that a constraint logic program P CLP can be built from the result of the path-length analysis of a Java bytecode program P and formally prove that if P CLP terminates then also P terminates. Hence a termination prover for constraint logic programs can be applied to prove the termination of P. We conclude with some discussion of the possibilities and limitations of our approach. Ours is the first existing termination analyser for Java bytecode dealing with any kind of data structures dynamically allocated on the heap and which does not require any help or annotation on the part of the user.

International audience; Musical scores annotation is a well-known practice from musicians, especially in educational terms. It consists in adding written comments to a score in order to make a phrase explicit and thus facilitate the learning of the piece and its performance. However, this practice raises knowledge transmission issues: how to share and preserve the information within the annotation without altering it? Indeed, the author is often the only person who knows rhe meaning of his annotations. As the use of digital tools constitutes a privileged way to solve this issue, we first explore the existing solutions for sharing performances through annotations, as well as their pros and cons. Then, we propose an optimized solution to annotate scores online in order to maintain the intent of the author, i.e. make it explicit to other performers through our tools. This proposition focuses on four main aspects of score annotation: the annotation nature, its symbolic and semantic representation, its indexation on the studied piece and at last, the communication structure that supports it.

International audience; no abstract