Mars 2015

Retour à la vue des calendrier
Lundi 2 Mars
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Open questions on Dynamic Semantic Annotation
Description: Ivan GARRIDO MARQUEZ Semantic annotation provides a powerful advantage for several
applications requiring text analysis. Semantic annotation requires the
presence of a semantic model to link the elements of the text to their
semantic representation. An a priori built ontology requires to be
maintained, adapted and to grow to keep its usefulness. When this update
is made along the annotation process, by exploiting the annotated text
to enrich the model we can discuss a dynamicity of the annotation. We
can identify two processes closely related with this dynamicity, the
knowledge acquisition and the annotation process itself. On this talk we
will try present an overview on this processes and how they have been
approached before.
Mardi 3 Mars
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Généralisation des nombres et polynômes de Bernoulli aux cas multiples
Description: Olivier Bouillot Les nombres et polynômes de Bernoulli sont des objets classiques qui apparaissent respectivement lors du prolongement analytique des fonctions zêta de Riemann et de Hurwitz aux entiers négatifs.En lien avec la généralisation multiple de ces fonctions, les multizêtas et multizêtas de Hurwitz, nous allons généraliser les nombres et polynômes de Bernoulli au cas multiple.Bien qu'il n'y a pas unicité d'une telle généralisation, nous introduirons un exemple explicite et satisfaisant où nombres de propriétés importantes des polynômes de Bernoulli se transmettent au cas multiple.Au passage, cela permet de répondre à une question sur la renormalisation des multizêtas aux entiers négatifs.
Mercredi 4 Mars
Heure: 09:30 - 10:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: On an Extension of Freeze LTL with Ordered Attributes
Description: Normann Decker We present an extension of Freeze LTL, a temporal logic equipped with registers,
over data words. Each position in a (multi-attributed) data word carries a
letter from a finite alphabet and assigns a data value to a fixed, finite set of
attributes. While reasoning on collections of data values is valuable for
expressing correctness properties of executions of dynamic programs the
satisfiability problem of Freeze LTL is undecidable if more than one register is
available or tuples of data values can be stored and compared arbitrarily. Our
extension therefore allows for specifying a dependency relation on attributes.
These dependencies introduce a restricted, yet flexible way of storing and
comparing collections of attribute values. This new dimension of flexibility is
orthogonal to, e.g., the number of registers or the available temporal
operators. In this setting we characterise precisely the type of dependency
relations that maintain decidability of the logic. To this end, we employ
reductions from and to nested counter systems. Moreover, by a complexity
theoretic characterisations we can show that our extension is strict and induces
a semantic hierarchy of logical fragments.
Vendredi 6 Mars
Heure: 11:00 - 12:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: The Plotkin's call-by-value lambda-calculus from a linear-logical viewpoint
Description: Giulio Guerrieri We translate the terms of ordinary lambda-calculus into proof-nets
accordingly the Girard's call-by-value "boring'' encoding of intuitionistic
implication A->B = !A-o!B. We show that (1) the Plotkin's call-by-value
beta-reduction is (bi)simulated in proof-nets via cut-elimination; (2)
there is a sequentialization theorem that characterizes all and only the
proof-nets which are translations of some lambda-term; (3) the equivalence
relation on lambda-terms which identifies lambda-terms having the same
translation in proof-nets is the call-by-value counterpart of Regnier's
sigma-equivalence and is not included in Plotkin's call-by-value
beta-equivalence. The semantics of lambda-terms is preserved by our
call-by-value sigma-equivalence.
Adding an oriented version of the call-by-value sigma-rules to the
call-by-value beta-reduction (and keeping the same syntax of ordinary
lambda-calculus) we preserve confluence and we get a call-by-value
operational characterization of solvable and potential valuable terms (this
is not possible in original Plotkin's call-by-value lambda-calculus).
Moreover, we give a semantic characterization of solvable and potential
valuable terms in a relational model, based on Linear Logic, satisfying the
Taylor expansion formula. As a technical tool, we also use a
resource-sensitive calculus in which the elements of the model are
Lundi 9 Mars
Heure: 14:00 - 15:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Sequence Classification Based on Delta-Free Sequential Patterns
Description: Pierre Holat Sequential pattern mining is one of the most studied and challenging tasks in data mining. However, the extension of well-known methods from many other classical patterns to sequences is not a trivial task. This talk presents a study of the notion of delta-freeness for sequences. While this notion has extensively been discussed for itemsets, the work described in this talk is the first to extend it to sequences. In this work, we define an efficient algorithm devoted to the extraction of delta-free sequential patterns. Furthermore, we show the advantage of the delta-free sequences and highlight their importance when building sequence classifiers, and we show how they can be used to address the feature selection problem in statistical classifiers, as well as to build symbolic classifiers which optimizes both accuracy and earliness of predictions.
Mardi 10 Mars
Heure: 12:30 - 13:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Multiband Robust Optimization: theory and applications
Description: Fabio D'Andreagiovanni Over the last years, Robust Optimization (RO) has emerged as an effective and efficient
methodology to tackle data uncertainty in real-world optimization problems. RO takes into
account data uncertainty in the shape of hard constraints that restrict the feasible set and
maintain only robust solutions, i.e. solutions that remain feasible even when the values of the
input data change.
In this talk, we provide an overview of our research about theory and applications of RO.
Specifically, we present Multiband Robustness, a new model for RO that we recently
proposed to generalize and refine the classical Gamma-robustness model by Bertsimas and
Sim. The main aim of our new model is to provide a refined representation of arbitrary non-
symmetric distributions of the uncertainty, that are commonly present in real-world
applications. Such refined representation grants a reduction in conservatism of robust
solutions, while maintaining the accessibility and computational tractability that have been a
key factor of success of Gamma-robustness. We also provide an overview of applications of
the Multiband model to real-world problems that we have considered in past and ongoing
research and industrial projects.
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Une généralisation des mots de Christoffel en dimension d.
Description: Sébastien Labbé In this work, we extend the definition of Christoffel words todirected subgraphs of the hypercubic lattice in arbitrary dimensionthat wecall Christoffel graphs. Christoffel graphs when $d=2$ correspond towell-known Christoffel words.We show that Christoffel graphs have similar properties to those ofChristoffel words: symmetry of their central part and conjugation withtheirreversal. Our main result extends Pirillo's theorem (characterization ofChristoffel words which asserts that a word $amb$ is a Christoffelword if andonly if it is conjugate to $bma$) in arbitrary dimension.In the generalization, the map $ambmapsto bma$ is seen as a flipoperation ongraphs embedded in $mathbb{Z}^d$ and the conjugation is a translation.We show that a fully periodic subgraph of the hypercubic lattice is atranslate of its flip if and only if it is a Christoffel graph.This is joint work with Christophe Reutenauer.Preprint is available at
Jeudi 12 Mars
Heure: 12:15 - 13:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Extraction de motifs graduels pour le résumé de données numériques
Description: Amal Oudni Les résumés linguistiques constituent une représentation linguistique décrivant
un ensemble de données numériques en phrases simples, compréhensibles et facilement interprétables.
Cet exposé se concentre sur les résumés linguistiques sous une forme particulière,
appelée motifs graduels, exprimant des corrélations de co-variations des valeurs
des attributs : on peut les illustrer pa r un exemple du type « plus l'âge du père
est avancé à la naissance des enfants, plus le risque d'autisme chez les enfants augmente ».

Lors de mon exposé, je présenterai trois types de contextualisation de ces motifs graduels.
Dans un premier temps, je décrirai le problème de motifs graduels contradictoires et une
nouvelle approche permettant d’éviter toute ambiguïté entre motifs validés.
Je présenterai ensuite la caractérisation des motifs graduels qui permet de faciliter
l'interprétation des motifs générés en grand nombre en introduisant une nouvelle clause
linguistiquement introduite par l'expression « surtout si ».
Je terminerai par la présentation d’une contextualisation qualifiant le mode de dépendances
graduelles, en introduisant la notion d'accélération par rapport aux autres attributs.

Pour chacune des formes de motifs enrichis extraits, je présenterai une formalisation
de la sémantique et l'interprétation souhaitées, des mesures de qualité pour évaluer
et quantifier la validité des motifs proposés, ainsi que des algorithmes efficaces
d'extraction automatique de ces motifs maximisant les critères de qualité définis.
Heure: 16:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Building Bridges Between Sets of Partial Orders
Description: Hernán Ponce de León Partial orders are a fundamental mathematical structure capable of representing concurrency and causality on a set of atomic events. In many applications it is essential to consider multiple partial orders, each representing a particular behavioral scenario or an operating mode of a modeled system.

In this talk I will present two mathematical formalisms capable of the compressed representation of sets of partial orders: Labeled Event Structures (LESs) and Conditional Partial Order Graphs (CPOGs). I will demonstrate their advantages and disadvantages and propose efficient algorithms for transforming of a set of partial orders from a given compressed representation in one formalism into an equivalent representation in another formalism without the explicit enumeration of each scenario. These algorithms make use of an intermediate mathematical formalism, which we call Conditional Labeled Event Structures (CLESs), that combines the advantages of LESs and CPOGs.

This is joint work with Andrey Mokhov (Newcastle University)
Vendredi 13 Mars
Heure: 11:00 - 12:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Functors are Type Refinement Systems
Description: Noam Zeilberger The standard reading of type theory through the lens of category
theory is based on the idea of viewing a type system as a category of
well-typed terms. In this joint work with Paul-André Melliès we propose a basic revision of this reading: rather
than interpreting type systems as categories, we describe them as
functors from a category of typing derivations to a category of
underlying terms. Then, turning this around, we explain how in fact
*any* functor gives rise to a generalized type system, with an
abstract notion of typing judgment, typing derivations and typing
rules. This leads to a purely categorical reformulation of various
natural classes of type systems as natural classes of functors.

In the talk I want to motivate and introduce this general framework
(which can also be seen as providing a categorical analysis of
_refinement types_), and as a larger example give a sketch of how the
framework can be used to formalize an elegant proof of a coherence
theorem by John Reynolds. If time permits, I will also describe some
of the natural questions raised by this perspective that are the
subject of ongoing research.
Mardi 17 Mars
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: ALEA, au CIRM (16-20 mars)
Description: Journées ALEA
Jeudi 19 Mars
Heure: 12:15 - 13:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Calcul efficace de la stabilité des concepts formels
Description: Sadok BEN YAHIA Dans l'ère des données massives, l'alliance de la qualité avec l'efficience pour la sélection des concepts formels « intéressants » serait une condition sine qua non. Dans ce cadre, la mesure de stabilité, de concepts formels, indiquerait dans quelle mesure l'intension de ce concept est liée à la présence d'objets particuliers dans son extension. Un concept stable possède, ainsi, une existence d'autant plus « réelle » que son intension ne dérive pas fortuitement d'une description bruitée de ses objets. Ainsi, les concepts stables sont très intéressants à localiser dans beaucoup de domaines puisqu'ils sont résistants au bruit, e.g., détection de communautés stables, classification par des classes monothétiques/ polythétiques.

Cependant, le calcul de la stabilité serait très couteux, ie., exponentiel en fonction de la taille de l'extension du concept. En effet, il faudrait explorer l'espace de tous les sous-ensembles de l'extension à la recherche qui restent fidèles à l'intension du concept formel.

Dans ce séminaire, nous passons en revue les très peu nombreux travaux qui se sont intéressés au calcul de la stabilité des concepts formels (organisés sous forme de treillis ou non). Ensuite, nous présentons des travaux récents sur l'exploitation des propriétés de monotonie et d'anti-monotonies des éléments clés dans l'espace de recherche. Ainsi, la saturation des cliques maximales non génératrices permet de traiter des espaces avoisinant les 215000. Nous montrons aussi que les identités d'inclusion/ exclusion servent au calcul efficace des stabilités des concepts formels organisés sous la forme d'un treillis.
Heure: 14:30 - 15:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Effective verification of low-level software with nested interrupts
Description: Lihao Liang Interrupt-driven software is difficult to test and debug, especially when
interrupts can be nested and subject to priorities. Interrupts can arrive
at arbitrary times, leading to an explosion in the number of cases to be
considered. We present a new formal approach to verifying interrupt-driven
software based on symbolic execution. The approach leverages recent
advances in the encoding of the execution traces of interacting, concurrent
threads. We assess the performance of our method on benchmarks drawn from
embedded systems code and device drivers, and experimentally compare it to
conventional formal approaches that use source-to-source transformations.
Our experimental results show that our method significantly outperforms
conventional techniques. To the best of our knowledge, our technique is the
first to demonstrate effective formal verification of low-level embedded
software with nested interrupts.

Joint work with
Daniel Kroening, Tom Melham, Peter Schrammel and Michael Tautschnig
Vendredi 20 Mars
Heure: 11:00 - 12:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: An infinitary model of linear logic
Description: Charles Grellois We construct an infinitary variant of the relational model of linear logic, where the exponential modality is interpreted as the set of finite or countable multisets. We explain how to interpret in this model the fixpoint operator Y as a Conway operator alternatively defined in an inductive or a coinductive way. We then extend the relational semantics with a notion of color or priority in the sense of parity games. This extension enables us to define a new fixpoint operator Y combining both inductive and coinductive policies. We conclude by sketching the connection between the resulting model of lambda-calculus with recursion and higher-order model-checking.
Mardi 24 Mars
Heure: 12:30 - 13:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Unit Commitment problems: approaches and solution algorithms
Description: Claudio Gentile The Unit Commitment is a the problem to manage a set of power generating units of different types over a short time horizon.
Unit Commitment is formulated as a Mixed Integer Nonlinear Programming problem. It requires special techniques to handle both the large size of the instances to be solved and the nonlinearity of the objective function.
Two main approaches have been used in its solution: the Lagrangian Relaxation coupled with primal heuristics and MILP approximations. We discuss some new advancements for both approaches.
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Automates d'arbres
Description: Gwendal Collet
Mercredi 25 Mars
Heure: 14:00 - 15:00
Lieu: Amphi A
Résumé: Extending Petri Nets with Object-Orientation
Description: Charles Lakos This seminar will introduce the formalism of Petri Nets and their use in modelling and analysing concurrent systems. It will briefly mention some of the extensions of Petri Nets to achieve greater descriptive comfort. It will then report on work over a number of years to extend Petri Nets with Object-Oriented features, thereby making it easier to define polymorphic modules and to capture incremental development. The seminar will also describe the properties of such nets and the analysis possibilities.
Mardi 31 Mars
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: TASEP
Description: Erik Aas