Séminaires du LIPN
Depuis 2007, plus de 1096 séminaires ont été présentés dans le laboratoire

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Séminaires à venir
LOVE 02/12/2021 Journée-Séminaire Chocola
 
ENS Lyon
02/12/2021    09:30 - 17:00
Résumé :
Séminaires passés
LOVE 29/11/2021 Guaranteed properties of dynamical systems under perturbations, par Jawher Jerray
Jawher Jerray, LIPN, Équipe LoVe  
Salle B107, bâtiment B, Université de Villetaneuse
29/11/2021    12:00 - 13:00
Résumé :
ince dynamical systems has a major impact on human development, especially critical systems that can put human lives at risk if something goes wrong. Hence, the need of studying the behavior of these systems in order to guarantee their correct functioning. Nevertheless, computing such type of system has never been an easy task, as the complexity of these systems is constantly increasing, in addition to the perturbations that may arise during their performance, as well as undefined parameters that may exist. To ensure that a system always produces the expected results and does not fail in any way, a formal verification of its behavior and properties is necessary. In this work, we study dynamical systems from different aspects and using various techniques. More specifically, we focus on the formal verification of some of its critical properties such as schedulability, synchronization, robustness and stability. In the first part, we study the schedulability of the flight control of a space launcher with unknown parameters and under constraints. Then, we propose a synthesis of the admissible timing values of the unknown parameters by a parametric timed model checker. We increase the complexity of the problem by taking into consideration the switch time between two threads. We extend this work by developing a tool that translates a given real-time system design into parametric timed automata in order to infer some timing constraints ensuring schedulability. In the second part, we study the stability of dynamical systems and the robustness of controls. We give a simple technique based on Euler's integration method which allows to build an invariant set around a given system. This technique guarantees that the approximate Euler solutions are attracted by a limit cycle. We apply the method on different systems, including chaotic systems with strange attractors. Furthermore, we show that a basic combination of a random sampling with a symbolic computation method assists to deal with robust control problems for nonlinear systems. Also, we illustrate a basic condition guaranteeing that a system with perturbation is robust under a repeated control sequence obtained by solving a horizon optimal control problem. Finally, we unified the main contributions of the second part in a tool called ORBITADOR which checks the stability of a given system and notably returns plots containing the evolution of the system in different views and the shape of the invariant if it exists.
LOVE 29/11/2021 A General Framework for Supervision of Opacity, par Nour SOUID
Nour SOUID, LIPN, Équipe LoVe  
Salle B107, bâtiment B, Université de Villetaneuse
29/11/2021    11:00 - 12:00
Résumé :
Opacity is a property of information flow that characterizes the ability of a system to keep an information secret from a third party called an attacker. In this paper, we investigate the problem of reinforcing the opacity using the Supervisory Control Theory. We present a novel approach to synthesize a supervisor to the system that prevents, at run time, a malicious observer from deducing secret information. Our approach is general since it does not take into consideration the relationship between the attacker's observation and the supervisor's one. Moreover, being based on formal methods, it allows us to represent various systems in different contexts. Particularly, we focus on web services and we apply our approach to a B2B (business-to-business) e-commerce use case.
AOC 25/11/2021 SMS++: a Structured Modelling System with ... hopefully, one day ... some useful application?, par Antonio Frangioni
Antonio Frangioni, Università di Pisa  
Salle B107, bâtiment B, Université de Villetaneuse
25/11/2021    10:30 - 11:30
Résumé :
On February this year, after about 8 years of gestation, an early beta release of the Structured Modelling System++ has been released to general public availability. SMS++ is a C++ library intended to facilitate the development of very large optimization problems with multiple nested heterogeneous structure, and especially of the corresponding solution methods, chiefly (but not exclusively) ones based on (parallel) decomposition. In the attempt of achieving this goal SMS++ has accrued a number of features that look quite unique in the landscape of modelling systems, so much so as to raise the legitimate suspicion that the reason why these features have never been developed before is because no sane person would have ever thought them a good idea. Yet the system is there and it does seem to offer some new viewpoints on mathematical modelling systems that may at least be worth a look. SMS++ is itself developed in an highly modular fashion and already counts a(n hopefully growing) number of separate sub-projects besides the "core" library and the support tools. One of these allows to solve Lagrangian Duals of complex integer programs with remarkable ease, and it will hopefully soon be joined by a similar component doing Benders' decomposition. Hence, there may actually be a few use cases in which SMS++ could be worth considering already, despite the very many missing components that would be needed to make it a really compelling prposition. In fact, perhaps the most interesting feature of SMS++ is it being community-oriented and (at least in principle) almost infinitely extendable to try to cater for the very diverse needs of the disparate clades of the optimization world. This alone may make it worth a second look, notwithstanding the arguably insane delusions of an all-conquering modelling system that some of the developers harbour and that would require capturing an unfeasibly large amount of mindshare to achieve.
LOVE 25/11/2021 Superpolynomial Lower Bounds Against Low-Depth Algebraic Circuits, par Nutan Limaye, Srikanth Srinivasan, Sebastien Tavenas
Nutan Limaye, Srikanth Srinivasan, Sebastien Tavenas, ITU Copenhagen, Aarhus University, CNRS & Université Savoie-Mont-Blanc  
Salle B107, bâtiment B, Université de Villetaneuse -- retransmis sur https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès 749983)
25/11/2021    10:00 - 11:00
Résumé :
An Algebraic Circuit for a polynomial PF[x1xN] is a computational model for constructing the polynomial P using only additions and multiplications. It is a syntactic model of computation, as opposed to the Boolean Circuit model, and hence lower bounds for this model are widely expected to be easier to prove than lower bounds for Boolean circuits. Despite this, we do not have superpolynomial lower bounds against general algebraic circuits of depth 3 (except over constant-sized finite fields) and depth 4 (over fields other than F2), while constant-depth Boolean circuit lower bounds have been known since the early 1980s. In this paper, we prove the first superpolynomial lower bounds against general algebraic circuits of all constant depths over all fields of characteristic 0 (or large). We also prove the first lower bounds against homogeneous algebraic circuits of constant depth over any field. Our approach is surprisingly simple. We first prove superpolynomial lower bounds for constant-depth Set-Multilinear circuits. While strong lower bounds were already known against such circuits, most previous lower bounds were of the form f(d)poly(N), where d denotes the degree of the polynomial. In analogy with Parameterized complexity, we call this an FPT lower bound. We extend a well-known technique of Nisan and Wigderson (FOCS 1995) to prove non-FPT lower bounds against constant-depth set-multilinear circuits computing the Iterated Matrix Multiplication polynomial IMMnd (which computes a fixed entry of the product of d nn matrices). More precisely, we prove that any set-multilinear circuit of depth computing IMMnd must have size at least ndexp(?O()) This result holds over any field, as long as d=o(logn). We then show how to convert any constant-depth algebraic circuit of size s to a constant-depth set-multilinear circuit with a blow-up in size that is exponential in d but only polynomial in s over fields of characteristic 0. (For depths greater than 3, previous results of this form increased the depth of the resulting circuit to (logs).) This implies our constant-depth circuit lower bounds. We can also use these lower bounds to prove a Depth Hierarchy theorem for constant depth circuits. We show that for every depth , there is an explicit polynomial which can be computed by a depth circuit of size s, but requires circuits of size s(1) if the depth is ?1. Finally, we observe that our superpolynomial lower bound for constant-depth circuits implies the first deterministic sub-exponential time algorithm for solving the Polynomial Identity Testing (PIT) problem for all small depth circuits using the known connection between algebraic hardness and randomness.
LOVE 22/11/2021 Can a single transition stop an entire Petri net?, par Prof. Dr. Jörg Desel
Prof. Dr. Jörg Desel, FernUniversität in Hagen  
Salle B107, bâtiment B, Université de Villetaneuse
22/11/2021    13:00 - 14:00
Résumé :
A transition stops a Petri net if, from any reachable marking, each occurrence sequence without this transition is finite. For bounded Petri nets it is easy to decide if a transition stops a net. We show that the coverability graph can be used to decide the property for unbounded Petri nets. A corresponding tool considers moreover generalisations of the above property.
LOVE 18/11/2021 Implementing the mwp-flow analysis, par Neea Rusch
Neea Rusch, University of Augusta  
Salle B107, bâtiment B, Université de Villetaneuse (retransmis sur https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24; code d'accès 749983)
18/11/2021    10:30 - 11:30
Résumé :
Jones and Kristiansen’s mwp-flow analysis certifies polynomial bounds on the size of the values returned by an imperative program. This method is compositional, extensible and elegant, as it bounds transitions between states instead of focusing on states in isolation. While simple to use, this theoretical result is difficult to prove correct and implement. Here we detail the challenges a naive implementation has to face, and how we remedied them to offer a fast, efficient and extended implementation of the technique. The result, pymwp, is a lightweight tool to automatically perform data-size analysis of C programs. This effort prepares and enables the development of certified complexity analysis, by transforming a costly analysis into a tractable program, that leverages compositionality and decorrelates the problem of finding the existence of a bound with its value.
AOC 18/11/2021 Optimization + Simulation: how to reduce bus bunching, par Yasmin A Rios Solis
Yasmin A Rios Solis, Escuela de Ingeniería y Ciencias - Campus Monterrey - Tecnológico de Monterrey, México  
ATTENTION Salle D215, bâtiment D, Université de Villetaneuse
18/11/2021    10:30 - 11:30
Résumé :
Real-time control strategies palliate with the day's dynamics in bus rapid transit systems. In this talk, we focus on a bus bunching problem that minimizes the number of buses of the same line cruising head-to-tail or arriving at a stop simultaneously by using bus holding times at the stops. For this, we propose a new mathematical model with quadratic constraints, whose objective function minimizes the penalties caused by buses that are bunching. Experimental results on a simulation of a bus rapid transit system in Monterrey, Mexico, show the efficiency of our approach. The results show a bus bunching reduction of 45% compared to the case without optimization. Moreover, in some scenarios the passenger waiting times are reduced by 30%.
LOVE 15/11/2021 Model Checking of Solidity Smart Contracts Adopted For Business Processes, par Ikram Garfatta
Ikram Garfatta, LIPN, Équipe LoVe  
Salle B107, bâtiment B, Université de Villetaneuse
15/11/2021    14:00 - 15:00
Résumé :
Several features of the Blockchain technology are well aligned with critical issues in the Business Process Management (BPM) field, and yet adopting Blockchain for BPM should not be taken lightly. In fact, the security of smart contracts, which are one of the main elements of the Blockchain that make the integration with BPM possible, has proved to be vulnerable. It is therefore crucial for the protection of the designed business processes to prove the correctness of the smart contracts to be deployed on a blockchain. In this talk, I will present our formal approach based on the transformation of Solidity smart contracts, with consideration of the BPM context in which they are used, into a Hierarchical Coloured Petri net. We express a set of smart contract vulnerabilities as temporal logic formulae and use the Helena model checker to, not only detect such vulnerabilities while discerning their exploitability, but also check other temporal-based contract-specific properties.
LOVE 15/11/2021 A Smart Software System for Fire Risk Notification, par Prof. Lars Michael Kristensen
Prof. Lars Michael Kristensen, Software Engineering Research Group - Western Norway University of Applied Sciences  
Salle B107, bâtiment B, Université de Villetaneuse
15/11/2021    13:00 - 14:00
Résumé :
Cold winter seasons result in very dry indoor conditions and have historically led to severe fires in the high and dense representation of wooden homes in Norway. To reduce fire conflagration probability and consequences, it is necessary to have an accurate estimate of the current and near future fire risk to take proper planning precautions. The DYNAMIC research project supported by the Norwegian Research Council has two main objectives: 1) to develop (mathematical) fire risk models that are able to quantify fire risk; 2) to investigate how cloud computing services providing access to weather data can be combined with recent developments in fire risk modelling to enable smart and fine-grained fire risk prediction services. The first part of the talk presents results from a first prototype implementation of a microservice-based fire risk notification system that has been experimentally validated at selected geographical locations in Norway. The system relies on weather data provided by cloud services of the Norwegian Meteorological Institute. Our experimental evaluation demonstrates the ability to provide trustworthy and accurate fire risk indications using a combination of recorded weather data and forecasts. Furthermore, our cloud- and micro-service software system implementation is efficient with respect to data storage and computation time. The second part of the talk presents work-in-progress on formal modelling and behavioural validation of the software architecture for the fire risk notification system.
RCLN 12/11/2021 Relation Extraction with Distant Supervision: noise Reductio, par Juan Luis Garcia-Mendoza
Juan Luis Garcia-Mendoza, Laboratorio de Tecnologias del Lenguaje, INAOE Puebla  
Salle B107, bâtiment B, Université de Villetaneuse
12/11/2021    12:30 - 13:45
Résumé :
Distant Supervision is an approach that allows automatic labeling of instances. This approach has been used in Relation Extraction. Still, the main challenge of this task is handling instances with noisy labels (e.g., when two entities in a sentence are automatically labeled with an invalid relation). The approaches reported in the literature addressed this problem by employing noise-tolerant classifiers. However, if a noise reduction stage is introduced before the classification step, this increases the macro precision values or keep the same values with fewer instances. An approach based on Adversarial Autoencoders is proposed to obtain a new representation that allows noise reduction in Distant Supervision.
LOVE 28/10/2021 Variable binding and substitution for (nameless) dummies, par Ambroise Lafont
Ambroise Lafont, University of Sydney  
Salle B107, bâtiment B, Université de Villetaneuse -- retransmis sur https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès 749983)
28/10/2021    10:30 - 11:30
Résumé :
By abstracting over well-known properties of De Bruijn's representation with nameless dummies, we design a new theory of syntax with variable binding and capture-avoiding substitution. We propose it as a simpler alternative to Fiore, Plotkin, and Turi's approach, with which we establish a strong formal link. We also show that our theory easily incorporates simple types and equations between terms. Joint work with Tom & Andre Hirschowitz, Marco Maggesi
LOVE 21/10/2021 [Séminaire Chocola] Program verification on a capability machine in the presence of untrusted code, par Armaël Guéneau
Armaël Guéneau, University of Aarhus  
https://chocola.ens-lyon.fr/events/online-2021-10-22/
21/10/2021    10:00 - 12:00
Résumé :
A capability machine is a kind of CPU with hardware support for fine-grained privilege separation. Practical designs and prototypes for such machines are seeing recent development as part of the CHERI project (University of Cambridge, SRI, ARM) (cheri-cpu.org, morello-project.org), making capability machines a promising target for designing and building new software with security in mind. In this talk, I will present some of the work done at Aarhus University and KU Leuven on developing formal principles for reasoning about security properties of code running on capability machines. I will show how one can prove functional correctness of programs that interact with untrusted (and possibly malicious) code while leveraging capabilities to protect their private state. The key aspects of this methodology are a program logic for reasoning about known code, and a logical relation providing a /universal contract/ of unknown code. The whole work has been mechanized in Coq using the Iris framework.
AOC 14/10/2021 Incorporating Holding Costs in Continuous-Time Service Network Design: New Model, Relaxation and Exact Algorithm, par Roberto Baldacci
Roberto Baldacci, Department of Electrical, Electronic, and Information Engineering “Guglielmo Marconi”, University of Bologna, Italy  
ATTENTION : Salle C311, bâtiment C, Université de Villetaneuse
14/10/2021    10:30 - 11:30
Résumé :
The continuous-time service network design problem (CTSNDP) occurs widely in practice. It aims to minimize the total operational cost by optimizing schedules of transportation services and routes of shipments for dispatching, which can occur at any time point along a continuous planning horizon. In order to be cost effective, shipments often wait to be consolidated, which incurs holding cost. Despite its importance, the holding cost has not been taken into account in the existing studies on the CTSNDP, since introducing it will significantly complicate the problem and make the solution development very challenging. To tackle this challenge, we develop a new dynamic discretization discovery algorithm, which can solve the CTSNDP with holding cost to exact optimum. The algorithm is based on a novel relaxation model and several new optimization techniques. Results from extensive computational experiments validate the efficiency and effectiveness of the new algorithm, as well as demonstrating the benefits that can be gained by taking into account holding costs in solving the CTSNDP. In particular, we show that the significance of the benefits depends on the connectivity of the underline physical network and the flexibility of the shipments’ time requirements.
LOVE 14/10/2021 Logique(s) linéaire(s) indexée(s) : syntaxe, structure et sémantique du fragment multiplicatif-additif, par Flavien Breuvart
Flavien Breuvart, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse -- retransmis sur https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès 749983)
14/10/2021    10:30 - 11:30
Résumé :
Nous allons décrire la logique linéaire indexée introduite par T.Ehrhard et A.Bucciarelli il y a 20 ans, expliquer en quoi cette logique est à la fois similaire à d'autres mais avec des particularités uniques. En particuliers nous verrons ses liens avec les logiques BLL-like avec aussi des exponentielles indexées. Dans un troisième temps nous expliquerons comment généraliser l'un et l'autre pour y greffer une notion abstraite de structure de ressources. Enfin, et selon les désir de l’audience, nous allons traiter l'aspect sémantique (catégorique et/or dénotationnel) du fragment additif de ces généralisation.
LOVE 30/09/2021 Call-by-Value, Again!, par Axel Kerinec
Axel Kerinec, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse -- retransmis sur https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès 749983)
30/09/2021    10:30 - 11:30
Résumé :
The quest for a fully abstract model of the call-by-value ?-calculus remains crucial in programming language theory, and constitutes an ongoing line of research. While a model enjoying this property has not been found yet, this interesting problem acts as a powerful motivation for investigating classes of models, studying the associated theories and capturing operational properties semantically. In this presentation we study a relational model presented as a relevant intersection type system, where intersection is in general non-idempotent, except for an idempotent element that is injected in the system. This model is adequate, equates many ?-terms that are indeed equivalent in the maximal observational theory, and satisfies an Approximation Theorem w.r.t. a system of approximants representing finite pieces of call-by-value Böhm trees. We show that these tools can be used for characterizing the most significant properties of the calculus – especially solvability. We also prove the decidability of the inhabitation problem for our type system. This is joint work with Simona Ronchi Della Rocca and Giulio Manzonetto, published at FSCD 2021.
AOC 23/09/2021 Design of diversified package tours for the digital travel industry : A branch-cut-and-price approach , par Laurent Alfandari
Laurent Alfandari, ESSEC  
Salle B107, bâtiment B, Université de Villetaneuse
23/09/2021    10:30 - 11:30
Résumé :
Motivated by the revolution brought by the internet and communication technology in daily life, this paper examines how the online travel agencies (OTA) can use these technologies to improve customer value. We consider the design of a fixed number of package tours offered to customers in the digital travel industry. This can be formulated as a Team Orienteering Problem (TOP) with restrictions on budget and time. Different from the classical TOP, our work is the first one to introduce controlled diversity between tours. This enables the OTA to offer tourists a diversified portfolio of tour packages for a given period of time, each potential customer choosing a single tour in the selected set, rather than multiple independent tours over several periods as in the classical TOP. Tuning the similarity parameter between tours enables to manage the trade-off between individual preferences in consumers’ choices and economies of scale in agencies’ bargaining power. We propose compact and extended formulations and solve the master problem by a branch-and-price method, and an alternative branch-cut-and-price method. The latter uses a delayed dominance rule in the shortest path pricing problem solved by dynamic programming. A particularity of the model is that in the column generation phase, the diversity constraints hold between each pair of columns, which is unusual and requires to generate these constraints on the fly. Our methods are tested over benchmark TOP instances of the literature, and a real dataset collected from a Chinese OTA. We explore the impact of tours diversity on all stakeholders, and assess the computational performance of the various approaches.
LOVE 16/09/2021 Physic-agnostic computational models, par Titouan Carette
Titouan Carette, LORIA & LRI  
Salle B107, bâtiment B, Université de Villetaneuse -- retransmis sur https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès 749983)
16/09/2021    10:30 - 11:30
Résumé :
Here is a (not so...) secret recipe to write a lot of papers: take any computational concept you like and add quantum, probabilistic, reversible, etc... before the name. In practice this is however not so easy, it often requires to start from scratch to find a formulation fitting our specific framework. Another way is to formulate the computational concept in an abstract language that can then be instantiated to the physical theory we have in mind. This can be done using category theory. An abstract computational process is represented by a string diagram and then interpretation functors provide semantics in various physical models. In this talk I will provide an example of such physic-agnostic model in the form of a diagrammatic approach to quantum streams. We will see that once we have designed the abstract graphical model, varying the physical theory can lead to interesting computational but also physical considerations.
LOVE 01/07/2021 [Séminaire Chocola] Milner and Alur walk into a bar, par Daniele Varacca
Daniele Varacca, LACL - Univ Paris Est Creteil  
https://chocola.ens-lyon.fr/events/online-2021-07-01/
01/07/2021    10:00 - 12:00
Résumé :
The chef kicks them out: "I'm sorry, in my kitchen we only use induction". This talk will start from Morris' PhD thesis in 1968 and present 50 years of theoretical computer science, through PCF, CCS, Alternating transition systems, contexts and strategies, ending up at the footsteps of the monumental Palace of Justice in Créteil.
LOVE 29/06/2021 Fault-tolerant LU factorization is low cost, par Daniel Torres Gonzalez
Daniel Torres Gonzalez, LIPN  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
29/06/2021    15:00 - 16:00
Résumé :
At large scale, failures are statistically frequent and need to be taken into account. Tolerating failures has arisen as a major challenge in parallel computing as the size of the systems grow, failures become more common and some computation units are expected to fail during the execution of a program. Algorithms used in these programs must be scalable, while being resilient to hardware failures that will happen during the execution. In this presentation, we present an algorithm that takes advantage of intrinsic properties of the scalable communication-avoiding LU algorithms in order to make them fault-tolerant and proceed with the computation in spite of failures. We evaluate the overhead of the fault tolerance mechanisms with respect to failure-free execution on both tall- and-skinny matrices (TSLU) and square matrices (CALU), and the cost of a failure during the execution.
LOVE 17/06/2021 [Séminaire Chocola] Focused nested calculi applied to the logic of bunched implications, par Sonia Marin
Sonia Marin, University College London  
https://chocola.ens-lyon.fr/events/online-2021-06-17/talks/marin/
17/06/2021    10:00 - 12:00
Résumé :
Focusing is a general technique for syntactically compartmentalising the non-deterministic choices in a proof system, which not only improves proof search but also has the representational benefit of distilling sequent proofs into synthetic normal forms. However, since focusing was traditionally specified as a restriction of the sequent calculus, the technique had not been transferred to logics that lack a (shallow) sequent presentation, as is the case for some modal or substructural logics. With K. Chaudhuri and L. Straßburger, we extended the focusing technique to nested sequents, a generalisation of ordinary sequents which allows us to capture all the logics of the classical and intuitionistic S5 cube in a modular fashion. This relied, following the method introduced by O. Laurent, on an adequate polarisation of the syntax and an internal cut-elimination procedure for the focused system which in turn is used to show its completeness. Recently, with A. Gheorghiu, we applied a similar method to the logic of Bunched Implications (BI), a logic that freely combines intuitionistic logic and multiplicative linear logic. For this we had first to reformulate the traditional bunched calculus for BI using nested sequents, followed by a polarised and focused variant that (again) we show is sound and complete via a cut-elimination argument.
LOVE 03/06/2021 [Séminaire Chocola] Internalizing Representation Independence with Univalence, par Carlo Angiuli
Carlo Angiuli, Carnegie Mellon University  
https://chocola.ens-lyon.fr/events/online-2021-06-03/talks/angiuli/
03/06/2021    15:00 - 17:00
Résumé :
In their usual form, representation independence metatheorems provide an external guarantee that two implementations of an abstract interface are interchangeable when they are related by an operation-preserving correspondence. In the dependently-typed setting, however, we would like to appeal to such invariance results within a language itself, in order to transfer theorems from simple to complex implementations. Homotopy type theorists have noted that Voevodsky's univalence principle equates isomorphic structures, but unfortunately many instances of representation independence are not isomorphisms. In this talk, we describe a technique for establishing internal relational representation independence results in Cubical Agda by using higher inductive types to simultaneously quotient two related implementation types by a heterogeneous correspondence between them. The correspondence becomes an isomorphism between the quotiented types, thereby allowing us to obtain an equality of implementations by univalence. Joint work with Evan Cavallo, Anders Mörtberg, and Max Zeuner. Available at https://dl.acm.org/doi/10.1145/3434293.
RCLN 31/05/2021 Knowledge-based Detection of Automatically Generated Text, par Vijini Liyanage
Vijini Liyanage, LIPN  
Salle A303, Bâtiment A, LIPN
31/05/2021    13:00 - 14:00
Résumé :
Séminaire de Vijini Liyanage, étudiante du groupe RCLN, qui va nous présenter son sujet de thèse et les premières étapes de sa thèse sur la détection des textes générés automatiquement par des modèles de langage neuronales, du genre GPT-2.
AOC 20/05/2021 Decomposition methods and column/matrix generation approaches for quadratic programming, par Lucas Létocart
Lucas Létocart, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse
20/05/2021    10:30 - 11:30
Résumé :
The purpose of this talk is to present three decomposition approaches for quadratic problems. First, we analyze a simplicial decomposition like algorithmic framework that handles convex quadratic programs in an effective way. We also propose a branch & bound approach based on this simplicial decomposition for the binary case and we introduce warmstart techniques using columns' projection. Then, we propose a methodological analysis on a family of reformulations combining Dantzig-Wolfe decomposition and Quadratic Convex Reformulation principles for binary quadratic problems. Finally, we propose a matrix generation method for quadratically constrained 0-1 quadratic problems based on a Dantzig-Wolfe reformulation. The domain of this relaxation corresponds to the Boolean Quadric Polytope.
LOVE 20/05/2021 [Séminaire Chocola] Monads, equational theories, and metrics for nondeterministic and probabilistic systems, par Valeria Vignudelli
Valeria Vignudelli, ENS Lyon  
https://chocola.ens-lyon.fr/events/online-2021-05-20/
20/05/2021    10:00 - 12:00
Résumé :
Monads and their presentations via equational theories provide a tool for reasoning about programs with computational effects. In recent works, we have studied monads resulting from the combination of nondeterminism, probabilities, and termination, as well as their extensions to the category of metric spaces. In this talk, we'll introduce this framework and show applications to proving equivalences and distances of nondeterministic and probabilistic systems. Bibliography: Bonchi, Sokolova, Vignudelli. The theory of traces for systems with nondeterminism and probabilities. LICS 2019. Available at: https://arxiv.org/abs/1808.00923 Mio, Vignudelli. Monads and quantitative equational theories for nondeterminism and probabilities. CONCUR 2020. Available at: https://arxiv.org/abs/2005.07509 Mio, Sarkis, Vignudelli. Combining nondeterminism, probability, and termination: equational and metric reasoning. LICS 2021. Available at: https://arxiv.org/abs/2012.00382
LOVE 06/05/2021 [Séminaire Chocola] Fixpoint Theory -- Upside Down, par Barbara König
Barbara König, Universität Duisburg-Essen  
https://chocola.ens-lyon.fr/events/online-2021-05-06/
06/05/2021    10:00 - 12:00
Résumé :
Knaster-Tarski's theorem, characterising the greatest fixpoint of a monotone function over a complete lattice as the largest post-fixpoint, naturally leads to the so-called coinduction proof principle for showing that some element is below the greatest fixpoint (e.g., for providing bisimilarity witnesses). The dual principle, used for showing that an element is above the least fixpoint, is related to inductive invariants. This talks considers proof rules which are similar in spirit but for showing that an element is above the greatest fixpoint or, dually, below the least fixpoint. The theory is developed for non-expansive monotone functions on suitable lattices of the form M^Y, where Y is a finite set and M an MV-algebra, and it is based on the construction of (finitary) approximations of the original functions. We show that our theory applies to a wide range of examples, including termination probabilities, behavioural distances for probabilistic automata and bisimilarity. Moreover it allows us to determine original algorithms for solving simple stochastic games.
AOC 22/04/2021 Extraction et partitionnement pour la recherche de régularités : application à l'analyse de dialogues., par Zacharie ALES
Zacharie ALES, ENSTA Paris | Institut Polytechnique de Paris  
Salle B107, bâtiment B, Université de Villetaneuse
22/04/2021    10:30 - 11:30
Résumé :
Dans le cadre de l'aide à l'analyse de dialogues, un corpus de dialogues peut être représenté par un ensemble de tableaux d'annotations encodant les différents énoncés des dialogues. Afin d'identifier des schémas dialogiques mis en œuvre fréquemment, nous définissons une méthodologie en deux étapes : extraction de motifs récurrents, puis partitionnement de ces motifs en classes homogènes constituant des régularités. Deux méthodes sont développées afin de réaliser l'extraction de motifs récurrents : LPCA-DC et SABRE. La première est une adaptation d'un algorithme de programmation dynamique tandis que la seconde est issue d'une modélisation formelle du problème d'extraction d'alignements locaux dans un couple de tableaux d'annotations. Le partitionnement de motifs récurrents est réalisé par deux formulations originales du problème de K-partitionnement sous la forme de programmes linéaires en nombres entiers. Lors d'une étude polyèdrale, nous caractérisons des facettes d'un polyèdre associé à ces formulations (notamment les inégalités de 2-partitions, les inégalités 2-chorded cycles et les inégalités de clique généralisées). Ces résultats théoriques permettent la mise en place d'un algorithme de plans coupants résolvant efficacement le problème. Nous développons le logiciel d'aide à la décision VIESA, mettant en œuvre ces différentes méthodes et permettant leur évaluation au cours de deux expérimentations réalisées par un expert psychologue. Des régularités correspondant à des stratégies dialogiques que des extractions manuelles n'avaient pas permis d'obtenir sont ainsi identifiées.
LOVE 22/04/2021 [Séminaire Chocola] The Time and Space of Interaction, par Gabriele Vanoni
Gabriele Vanoni, Università di Bologna  
https://chocola.ens-lyon.fr/events/online-2021-04-22/
22/04/2021    10:00 - 12:00
Résumé :
Girard's Geometry of Interaction (GOI) can be made concrete by considering it as an implementation technique for functional programs, in particular the lambda calculus. Our work is about the complexity analysis of the abstract machine based on the GOI, the interaction abstract machine (IAM). We have adapted in a non trivial way de Carvalho's non idempotent intersection types so that type derivations completely characterize the time and space complexity of the IAM, thus providing a logical account of the IAM resource usage. Moreover, by the way of the type systems we have introduced, we are able to state some negative results about time and space cost models for the lambda calculus based on the IAM. This is joint work with Beniamino Accattoli and Ugo Dal Lago.
AOC 15/04/2021 Formulations PLNE pour un problème d'ordonnancement juste-à-temps, par Anne-Elisabeth FALQ
Anne-Elisabeth FALQ, Sorbonne université, CNRS, LIP6, équipe RO  
Salle B107, bâtiment B, Université de Villetaneuse
15/04/2021    10:30 - 11:30
Résumé :
Une contrainte essentielle pour un problème d'ordonnancement sur une machine est le non-chevauchement des tâches: deux tâches ne peuvent être exécutées en même temps. Les premières inégalités de non-chevauchement ont été proposées par Queyranne (1993) pour le problème de minimisation de la somme pondérée des dates de fins. La famille d'inégalités linéaires proposée décrit exactement l'enveloppe convexe des vecteurs encodant des ordonnancements réalisables par les dates de fins des tâches. Ces inégalités ne coupent pas tous les vecteurs encodant un ordonnancement avec chevauchement mais assurent le non-chevauchement au sens où tous les points extrêmes du polyèdre qu'elles définissent encodent des ordonnancements réalisables, et plus précisément ceux calés à gauche qui forment un ensemble dominant pour ce problème. Dans cet exposé, nous nous intéresseront particulièrement au problème d'ordonnancement juste-à-temps où toutes les tâches partagent une même date d'échéance commune et où il s'agit de minimiser la somme pondérée des avances et des retards par rapport à cette date. En s'appuyant sur les propriétés de dominance connues pour ce problème NP-difficile (Hall et Posner, 1991), nous proposerons une formulation basée sur des inégalités de non-chevauchement nouvelles. Cette formulation, qui n'est pas exactement un programme linéaire en nombre entiers (PLNE) puisqu'elle fait apparaître des contraintes d'extremalité, peut être résolue par un solveur de PL implémentant un algorithme de "Branch-and-Cut". Nous expliquerons comment et présenterons quelques résultats expérimentaux. Dans un second temps, nous proposerons une formulation compacte pour ce problème, que nous renforçons par des inégalités dites de dominance. Ces inégalités sont ainsi nommées car elles traduisent la dominance des solutions localement optimales, où local s'entend pour un voisinage généré par une famille d'opérations sur les solutions. Pour chaque opération considérée, une inégalité élimine les solutions qu'on pourrait améliorer en appliquant la transformation. De ce fait, ces inégalités coupent des point entiers, et diffèrent en cela des inégalités classiques de renforcement. Grâce à des résultats expérimentaux, nous montrerons le gain d’efficacité qu'apporte ces inégalités de dominance.
LOVE 15/04/2021 Categorifying Non-Idempotent Intersection Types, par Giulio Guerrieri
Giulio Guerrieri, University of Bath  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
15/04/2021    10:00 - 11:00
Résumé :
Non-idempotent intersection types can be seen as a syntactic presentation of a well-known denotational semantics for the lambda-calculus, the category of sets and relations. Building on previous work, we present a categorification of this line of thought in the framework of bang calculus, an untyped version of Levy's call-by-push-value. We define a bicategorical model for the bang calculus, whose syntactic counterpart is a suitable category of types. In the framework of distributors, we introduce intersection type distributors, a bicategorical proof relevant refinement of relational semantics. Finally, we prove that intersection type distributors characterize normalization at depth 0. This is joint work with Federico Olimpieri, published at CSL 2021.
LOVE 08/04/2021 [Séminaire Chocola] Sketching type theories, par Daniel Gratzer
Daniel Gratzer, Aarhus University  
https://chocola.ens-lyon.fr/events/online-2021-03-25/
08/04/2021    10:00 - 12:00
Résumé :
Recent developments in type theory have attempted to systematically recast properties of the syntax of a type theories (canonicity, normalization, etc.) into equivalent questions about the category of models. This dictionary relies on a formal link between the syntax of a theory and its category of models: the syntax of the theory must organize into an initial model. To expedite this process, several logical frameworks have been proposed which provide schemata for defining a type theory so that it automatically determines a category of models in which syntax is initial. In this talk, rather than giving a new logical framework per se, we propose a new discipline for creating logical frameworks based around finitary 2-monads and sketches. As a case study of this approach, we show how locally Cartesian closed categories provide a suitable doctrine for type theories. We illustrate how a general theory of sketches [KPT99] can be used to define syntactic categories for type theories in a style that resembles the use of Martin-Löf's Logical Framework [NPS90], following the "judgments as types" principle [HHP93, ML87]. We prove a semantic adequacy result for locally Cartesian closed categories relative to Uemura's representable map categories [Uem19]: if a theory is definable in the framework of Uemura, the locally Cartesian closed category that it generates is a conservative (fully faithful) extension of its syntactic representable map category. On this basis, we argue for the use of locally Cartesian closed categories as a simpler alternative to Uemura's representable map categories. This is joint work with Jonathan Sterling, and a preprint is available on arxiv: https://arxiv.org/abs/2012.10783
LOVE 07/04/2021 Approche formelle pour la vérification formelle de la composition de logiciels, par Mohamed Graiet
Mohamed Graiet  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
07/04/2021    09:00 - 10:00
Résumé :
La réutilisation est un concept clé dans la construction de systèmes logiciels. Elle permet de composer un ensemble de logiciels existants pour construire de nouveaux logiciels à valeur ajoutée. Dans le contexte de notre travail, on s'intéresse à la composition de deux types de logiciels, à savoir les services Web et logiciels libres à base de packages FOSS (Free and Open Source Software). La vérification de la correction de la composition pour la sécurité de logiciels FOSS et de services Web reste l’une des tâches les plus difficiles malgré les efforts et les travaux de recherches entrepris. Un service composé est déclaré correct s’il respecte un ensemble d’exigences de deux types: les exigences transactionnelles et de QoS (la sécurité des exigences métiers). Les exigences de QoS sont définies sous la forme d’un contrat SLA (service-level agreement). Un contrat SLA est un ensemble de contraintes de QoS. Les exigences transactionnelles sont spécifiées par les concepteurs en utilisant le concept d’états de terminaison acceptés (ETA). Un logiciel composite FOSS est dit correct s’il respecte un ensemble de contraintes de dépendances et de capacités. Pour parvenir à résoudre ce problème de vérification, nous proposons une approche formelle fondée sur la méthode Event-B. Une telle approche se résume en deux points: i) Une formalisation Event-B de la composition de services avec Event-B. ii) Une formalisation Event-B de la composition de logiciels FOSS dans un contexte cloud. Ces deux formalisations sont validées en se servant des obligations de preuves et d’un model-checker ProB. La formalisation de la composition de services se repose sur les trois étapes suivantes: - Etape 1: formalisation des services Web. - Etape 2: formalisation de la composition statique de services Web. - Etape 3: formalisation de la composition dynamique de services Web. Quant à la deuxième formalisation, elle est construite en deux étapes principales. La première étape concerne la formalisation des logiciels FOSS composites d’une manière générale. Dans la deuxième étape, on raffine cette formalisation par l’introduction des propriétés d’élasticité verticale et horizontale offertes par l'environnement cloud. La propriété d'élasticité verticale permet d'augmenter ou de réduire la capacité des logiciels en ajoutant de nouvelles ressources (logiciels) ou en supprimant celles qui ne sont pas en cours d’utilisation. La propriété d'élasticité horizontale permet d'augmenter ou de diminuer les ressources logicielles en ajoutant de nouvelles copies de composants existants ou en supprimant les inutiles. Pour la mise en œuvre de cette approche nous utilisons une approche à base d’IDM (transformation texte to modèle, modèle to modèle et modèle to texte).
LOVE 01/04/2021 Typing Differentiable Programming, par Marie Kerjean
Marie Kerjean, LIPN, CNRS & Université Sorbonne Paris Nord  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
01/04/2021    10:15 - 11:15
Résumé :
Differentiable programming is a recent research area: its objective is to express differentiation as a modular algorithmic transformation on rich programming languages. It is in particular motivated by the various applications of automatic differentiation in machine learning or formal calculus. In this talk I will present joint work with Pierre-Marie Pédrot, focusing on the typing system used to express differentiation. We will first review a few examples of differentiable languages recently exhibited in the literature. This allows to identity the linear Dialectica transformation as a reverse automated differentiation transformation on a higher-order lambda-calculus with positive types. Building on the intuitions provided by Dialectica and distribution theory, we construct a lambda-calculus with an internal differentiation operator. This calculus is typed by a type system inspired by Differential Linear Logic. Noticeably, we are able to express backward automatic differentiation as an evaluation strategy.
LOVE 30/03/2021 Reducing the Security Assessment for Industrial Cyber-Physical Systems against Smart Attacks , par Samir Ouchani
Samir Ouchani, Lineact CESI (Aix-en-Provence, France)  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
30/03/2021    10:30 - 11:30
Résumé :
Industrial cyber-physical systems (ICPS) are heterogeneous inter-operating parts that can be physical, technical, networking, and even social-like agent operators. Incrementally, they perform a central role in critical and industrial infrastructures, governmental, and personal daily life. Especially with the Industry 4.0 revolution, they became more dependent on connectivity by supporting novel communication and distance control functionalities, which expand their attack surfaces that result in a high risk for cyber-attacks. Further, regarding physical and social constraints, they may push up new classes of security breaches that might result in serious economic damages. Thus, designing a secure ICPS is a complex task that has to guarantee security and harmonize the functionalities between the various parts that interact with different technologies. This talk highlights the significance of cyber-security infrastructure and shows how to evaluate, prevent, and mitigate ICPS-based cyber-attacks. First, I will take this opportunity to introduce myself and briefly present my ongoing research activities. Then, I will present the foundation of a prominent semantics for ICPS’s entities and their composition, which includes social actors that act differently than mobile robots and automated processes. In addition, I will provide the feasible attacks generated by a reinforcement learning mechanism based on multiple criteria that selects both appropriate actions for each ICPS component within the possible countermeasures for mitigation. Finally, I will detail the overall solution that reduces the verification cost and its effectiveness in a real use case scenario.
LOVE 19/03/2021 Avancées récentes sur les algèbres de Kleene concurrentes, par Paul Brunet
Paul Brunet, University College London  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
19/03/2021    10:30 - 11:30
Résumé :
Les algèbres de Kleene concurrentes (CKA) fournissent un cadre algébrique pour raisonner sur les programmes concurrents. Au cours de ces dernières années, nous avons étudié différentes manières d'enrichir ce modèle afin de capturer une classe plus large de problèmes de vérification. Dans cet exposé, je présenterai tout d'abord les bases de CKA, avec ses présentations axiomatiques et combinatoires, et les résultats de décidabilité correspondants. Je ferais ensuite un bref panorama de certaines extensions du modèle, en considérant des aspects tels que le flot de contrôle, la cohérence des accès mémoire, et l'exclusion mutuelle. Ce travail est le fruit de collaborations avec Tobias Kappé, Jana Wagemaker, Simon Docherty, Fabio Zanasi, Jurriaan Rot, Alexandra Silva, David Pym, Damien Pous, et Georg Struth.
LOVE 19/03/2021 Modeling and formal verification of a communicating autonomous vehicle system, par Johan Arcile
Johan Arcile  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
19/03/2021    09:00 - 10:00
Résumé :
A system of autonomous vehicles consists of several agents individually making decisions in real time while exchanging information with other agents nearby. The validation of formal logic properties in such systems is not possible through naive approaches, due to the large number of variables involved in their representation. The two complementary works that will be presented have been developed to address this issue: - The VerifCar software framework, dedicated to decision-making analysis of communicating autonomous vehicles, which uses the state-of-art tool Uppaal. - The formalism of MAPTs and its dedicated exploration algorithms, allowing the use of heuristics that reduces the computation time needed to address reachability problems.
LOVE 18/03/2021 Model-checking pour l’agriculture de précision, par Rim Saddem
Rim Saddem  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
18/03/2021    14:00 - 15:00
Résumé :
Dans cette présentation, je vais vous présenter mon travail de recherche qui comporte deux parties : la première porte sur ce que j’ai effectué durant ma thèse et la deuxième porte sur ce que j’ai effectué durant mon poste ATER. Mon travail de thèse porte sur l’application des techniques de model-checking pour résoudre des problèmes issus de l’agriculture de précision. L’agriculture de précision (AP) s’est fortement développée au cours des dernières décennies avec les progrès des technologies de localisation, des capteurs et des techniques de télédétection. Le principe de l’AP est de rechercher et mettre en œuvre la Bonne action au Bon moment et au Bon endroit ("3B"), avec l’objectif d’améliorer l’efficience de l’agriculture suivant les critères d’une agriculture durable. Pour modéliser et vérifier des opérations agricoles, une représentation des dynamiques temporelles et spatiales est nécessaire. Le model- checking de systèmes d’automates temporisés avec des requêtes dans une logique temporelle arborescente répond à ces besoins, les positions spatiales pouvant être représentées de façon ad-hoc dans le cadre de ces formalismes. Trois exemples d’opérations agricoles ont été considérés dans ce travail. La première est relative au calcul d’une séquence optimale de commandes pour une pulvérisation de précision en viticulture. La seconde concerne la récolte sélective en viticulture. La dernière est relative à la vérification d’une mission de robotique agricole. Nous étudions dans ces exemples l’atteignabilité d’un état cible pour l’opération, ou l’atteignabilité avec un critère de coût optimal. Pour pallier au problème d’explosion combinatoire rencontré dans les cas traités, une méthodologie de décomposition pour le model-checking d’atteignabilité a été développée. Les résultats expérimentaux avec et sans décomposition sont présentés pour les 3 exemples d’opération étudiés. La technique de décomposition est appliquée sur 2 des 3 exemples et les résultats expérimentaux montrent son efficacité. Mon travail durant mon poste ATER propose une extension du formalise des processus métiers pour prendre en considération la représentation spatiale afin de modéliser le comportement des robots.
LOVE 18/03/2021 Transcendental Syntax: the dynamics of logic programs and tilings, applied to Linear Logic, par Boris Eng
Boris Eng, LIPN, Université Sorbonne Paris Nord  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
18/03/2021    10:00 - 11:00
Résumé :
The Transcendental Syntax, successor of Girard's Geometry of Interaction programme, aims at a reconstruction of linear logic from computation with finite objects. We define a model of computation we call Stellar Resolution; a graph-theoretical reformulation of Robinson's first-order resolution, which appear to be closely related to geometric tilings. As a first illustration of the Transcendental Syntax's technical content, we show that we can naturally encode both the cut-elimination and logical correctness of MLL proof-structures. Using techniques from realisability, similarly to ludics, we retrieve a very generic notion of linear typing as a description of computational behaviour for programs computing with local and asynchronous interactions.
AOC 17/03/2021 A snapshot of quantum algorithms for optimization, par Giacomo Nannicini
Giacomo Nannicini, IBM - Watson  
Salle B107, bâtiment B, Université de Villetaneuse
17/03/2021    15:00 - 16:00
Résumé :
There is much hype surrounding quantum computing and its potential applications for optimization. However, the technical details are often lost in translation. In this talk I will give an overview of quantum algorithms that may - one day - be useful for continuous and discrete optimization, highlighting possible sources of advantage as well as limitations. In particular, I will discuss variational hybrid algorithms for optimization, simulated annealing for counting problems, algorithms for linear systems, and algorithms for SDPs and LPs. I assume no prior knowledge of quantum mechanics.
AOC 11/03/2021 Learning to solve the single machine scheduling problem with release times and sum of completion times, par Axel Parmentier
Axel Parmentier, ENPC  
Salle B107, bâtiment B, Université de Villetaneuse
11/03/2021    10:30 - 11:30
Résumé :
In this work, we focus on the solution of a hard single machine scheduling problem by new heuristic algorithms embedding techniques from machine learning field and scheduling theory. These heuristics transform an instance of the hard problem into an instance of a simpler one solved to optimality. The obtained schedule is then transposed to the original problem. Computational experiments show that they are competitive with state-of-the-art heuristics, notably on large instances.
LOVE 11/03/2021 [Séminaire Chocola] Machine-Checked Computer-Aided Mathematics, par Assia Mahboubi
Assia Mahboubi, INRIA  
https://chocola.ens-lyon.fr/events/seminaire-2021-03-11/
11/03/2021    10:00 - 12:00
Résumé :
This talk presents an overview of three contributions to the formal verification of mathematics in dependent type theory. The first of these contributions deals with the realization of a library of digitized mathematics, covering the standard undergraduate background in algebra as well as some more advanced chapters in finite group theory. The two other contributions are related to the issues pertaining to the formal verification of computational mathematical proofs, by the means of symbolic algorithms and of rigorous numerical methods respectively. We conclude with a few perspectives on the formal verification of computer-aided mathematics.
LOVE 05/03/2021 Contributions to Boolean satisfiability solving and its application to the analysis of discrete systems, par Souheib Baarir
Souheib Baarir, LIP6 - Université de Paris Nanterre  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
05/03/2021    14:00 - 15:30
Résumé :
Despite its NP-Completeness, propositional (Boolean) satisfiability (SAT) covers a broad spectrum of applications. Nowadays, it is an active research area finding its applications in many contexts: planning decision, cryptology, computational biology, hardware and software analysis, etc. Hence, the development of approaches that could handle increasingly challenging SAT problems has become a focus. During these last 8 years, SAT solving has been the main subject of my research work, and in this talk I will present some of the main results we obtained in the field.
LOVE 05/03/2021 On the formal verification of safety-critical systems: challenges, approaches and perspectives, par Mohammed Foughali
Mohammed Foughali, VERIMAG  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
05/03/2021    12:15 - 13:45
Résumé :
Safety-critical applications, e.g. those stemming from robotic, autonomous and cyber-physical systems, must be formally verified against crucial behavioral and timed properties. Yet, the use of formal verification techniques in such context faces a number of challenges, such as the absence of formal foundations of robotic frameworks and the lack of scalability of exhaustive verification techniques. In this talk, I will explore the approaches I have been proposing for the last six years to tackle these challenges, based on a global vision that favors correctness, user-friendliness and scalability of formal methods vis-à-vis real-world robotic and autonomous systems deployed on embedded platforms. I will discuss a major part of my work where safety-critical specifications are automatically translated into strictly equivalent formal models on which model checking, but also scalable non exhaustive techniques such as statistical model checking and runtime verification, may be used by practitioners to gain a considerable amount of trust in their underlying applications. Further, I will present a couple of techniques that allow to take into account hardware and OS specificities in the verification process, such as the scheduling policy and the number of processor cores provided by the platform, and thus increase the meaningfulness of the verification results. I will conclude with possible future research directions within the broad objective of deploying trustable safety-critical systems through bridging the gap between the software engineering, robotics, formal methods and real-time systems communities.
LOVE 04/03/2021 Geometry of Interaction for ZX-Diagrams, par Kostia Chardonnet et Renaud Vilmart
Kostia Chardonnet et Renaud Vilmart, LRI  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
04/03/2021    10:30 - 11:30
Résumé :
ZX-Calculus is a versatile graphical language for quantum computation equipped with an equational theory. Getting inspiration from Geometry of Interaction, in this work we propose a token-machine-based asynchronous model of both pure ZX-Calculus and its extension to mixed processes. We also show how to connect this new semantics to the usual standard interpretation of ZX-diagrams. This model allows us to have a new look at what ZX-diagrams compute, and give a more local, operational view of the semantics of ZX-diagrams.
LOVE 25/02/2021 [Séminaire Chocola] Titre bientôt disponible, par Zeinab Galal
Zeinab Galal, IRIF, Université de Paris  
http://chocola.ens-lyon.fr/events/online-2021-02-25/
25/02/2021    10:00 - 12:00
Résumé :
AOC 18/02/2021 Combinatorial Optimization Theory and Algorithms for Set Packing and Location Problems, par Mercedes Pelegrin
Mercedes Pelegrin, LIX  
Salle B107, bâtiment B, Université de Villetaneuse
18/02/2021    10:30 - 11:30
Résumé :
In this talk, we will cover modeling for two optimization problems, as well as Mathematical Programming methods that can be applied to solve them. The first part will be devoted to the set packing problem, one of the seminal problems in Combinatorial Optimization. We will focus on generating hyperplanes to describe the set packing polytope. Namely, we will present a new lifting theorem and illustrate its application to facility location. In the second part of the talk, we will address the problem of identifying a group of key nodes in a network. We will propose a mixed integer nonlinear program (MINLP) that embeds eigenvector centrality in a clustering partition. The resulting model uncovers the group of key nodes (the clusters centroids) and their communities (the clusters). Modeling this idea involves nonlinear equations, which will be linearized to produce a mixed integer linear program (MILP). Symmetry breaking, a recurrent topic in Combinatorial Optimization, will be also addressed. Computational results on synthetic and real-life networks will be presented.
LOVE 18/02/2021 Enriched concurrent games: witnesses for proofs and resource analysis, par Aurore Alcolei
Aurore Alcolei, Università di Bologna  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
18/02/2021    10:00 - 11:00
Résumé :
Game semantics is known as the semantics of control flow and interactions. Among its various models, causal game models emphasize the causal relation between the computational events that describe these interactions. This view point is particularly suitable to represent parallel computations and concurrent behaviours. In this talk I will show how causal game models can be enriched with annotations in order to capture side computations, that are, computational information that varies with the control flow but does not affect it. This enrichment will motivated through two semantics problems in both logics and programming: - Offering a novel compositional interpretation of Herbrand theorem by capturing the structure of Herband witnesses as causal strategies annotated with terms; - Enriching a sound and adequate concurrent game model for higher order concurrent programs with quantitative information in order to reflect their minimal execution time.
AOC 11/02/2021 Linearization techniques for MINLP, par Sandra Ulrich Ngueveu
Sandra Ulrich Ngueveu, LAAS-CNRS  
Salle B107, bâtiment B, Université de Villetaneuse
11/02/2021    10:30 - 11:30
Résumé :
We review state-of-the-art linearization and approximation techniques for the solution of non-linear mixed-integer programs. We show in particular how to ensure an a priori guarantee on the quality/feasibility of the solution, a reduction of the size of the converted problem and a minimization of the computing time. We then present an iterative method for the solution of a class of non-linear mixed-integer programs to arbitrary numerical precision. By keeping the scope of the update local from one iteration to another, the computational burden is only slightly increased from iteration to iteration. As a consequence, our method presents very nice scalability properties and is little sensitive to the desired precision. We assess its efficiency for approximating the non-linear variants of three problems: the uncapacitated facility location problem, the multi-commodity network design problem, and the transportation problem. Our results indicate that, as the desired precision becomes smaller, our approach can lead to significant gains in computing times, often being orders of magnitude faster than a baseline method, and scales to approximate larger problems.
LOVE 11/02/2021 [Séminaire Chocola] Sequentiality, References and Well-bracketing in the pi-calculus, par Enguerrand Prebet
Enguerrand Prebet, ENS Lyon  
http://chocola.ens-lyon.fr/events/online-2021-02-11/
11/02/2021    10:00 - 12:00
Résumé :
The pi-calculus is used as a model for programming languages. Its contexts exhibit arbitrary concurrency, making them very discriminating. This may prevent validating desirable behavioural equivalences in cases when more disciplined contexts are expected. We formalise using types three different disciplines: sequentiality or the idea of having a single thread of computation ; reference types for which channels behave like bits of store or atomic register ; and well-bracketing which strengthens the sequentiality constraints to also obey a stack-like discipline. For each, we present the type system along with its consequences on behavioural equivalence and the corresponding bisimulation techniques.
LOVE 09/02/2021 Symbolic Verification Techniques for Multiparty Interaction, par Carlos Olarte
Carlos Olarte, Federal University of Rio Grande do Norte (Brazil)  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
09/02/2021    12:00 - 13:00
Résumé :
Multiparty interactions are commonplace in today's distributed systems. An agent usually communicates, in a single session, with other agents to accomplish a given task. Take for instance an online transaction including the credit card system, the vendor and the client. What we observe is a single transaction composed of several (binary) interactions leading to changes in the state of all the involved agents. Multiway synchronization process calculi, that move from a binary to a multiparty synchronization discipline, have been proposed to formally study the behavior of those systems. For instance, the Core Network Algebra (CNA) extends the point-to-point communication discipline of Milner's CCS with link-chains, describing how information flows among the agents. In this model, the number of participants in an interaction cannot be fixed a priori, and hence, CNA computations are inherently non-deterministic. This leads to an exponential blow-up in the number of reachable states and makes it difficult to devise verification techniques for this formalism. In this talk, I will show four mechanisms that we have proposed for tackling this problem. Namely: (1) A symbolic semantics and bisimulation for CNA that are more amenable for automated reasoning. Symbolic configurations represent, compactly, a possibly infinite number of states and they can be effectively checked. (2) The Symbolic Link Modal Logic, a smooth extension of Hennessy-Milner logic that faithfully characterizes the (symbolic) transitions of CNA processes. (3) An extension of CNA with constraints that declaratively allow the modeler to restrict the interactions that should actually happen. Our definition of constraints is general enough, and it offers the possibility of accumulating costs in multiparty negotiations. This extension finds applications in the modeling of Service Level Agreement protocols and balancing the interactions in a concurrent system. (4) A suitable representation of the above techniques as an executable rewrite theory. Our implementation of this theory in Maude offers the possibility of animating CNA specifications, and it provides (automatic) verification procedures to analyze them.
LOVE 04/02/2021 A uniform framework for substructural logics with modalities , par Elaine Pimentel
Elaine Pimentel, Universidad Federal del Rio Grande do Norte  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
04/02/2021    14:00 - 15:00
Résumé :
In this work we investigate such a local system for linear logic (LL) based on linear nested sequents (LNS). Relying on that system, we propose a general framework for modularly describing systems combining, coherently, substructural behaviors inherited from LL with simply dependent multimodalities. This class of systems includes linear, elementary, affine, bounded and subexponential linear logics and extensions of multiplicative additive linear logic (MALL) with normal modalities, as well as general combinations of them. (joint work with Björn Lellmann and Carlos Olarte).
AOC 28/01/2021 Postier chinois dans les triangulations planaires et applications à la chimie, par Matej Stehlik
Matej Stehlik, INP Grenoble  
Salle B107, bâtiment B, Université de Villetaneuse
28/01/2021    10:30 - 11:30
Résumé :
Le problème du postier chinois est un problème classique de l’optimisation combinatoire. Dans cet exposé, je me concentrerai sur le problème du postier chinois dans les triangulations planaires. Je montrerai une borne optimale sur la longueur du plus court parcours de postier, et je discuterai des liens à la chimie théorique.
LOVE 28/01/2021 [Séminaire Chocola] Stable Relations and Abstract Interpretation of Higher-Order Programs, par Benoît Montagu
Benoît Montagu, INRIA  
http://chocola.ens-lyon.fr/events/online-2021-01-28/
28/01/2021    10:00 - 12:00
Résumé :
We present a novel denotational semantics for the untyped call-by-value ?-calculus, where terms are interpreted as stable relations, i.e. as binary relations between substitutions and values, enjoying a monotonicity property. The denotation captures the input-output behaviour of higher-order programs, and is proved sound and complete with respect to the operational semantics. Following the principles of abstract interpretation, we use our denotational semantics as a collecting semantics to derive a modular relational analysis for higher-order programs. The analysis infers equalities between the arguments of a program and its results---a form of frame condition for functional programs.
LOVE 26/01/2021 Vérification formelle de systèmes distribués et de leurs propriétés réseau, par Nicolas SCHNEPF
Nicolas SCHNEPF  
Salle A303
26/01/2021    12:00 - 13:30
Résumé :
L’emploi de méthodes formelles est aujourd’hui plus que jamais nécessaire pour assurer la vérification ou la synthèse de politiques réseau assurant les propriétés de sûreté et de sécurité requises par les systèmes distribués contemporains. Dans cet exposé je présenterai mes travaux de thèse autour de l’orchestration et de la vérification formelle de fonctions de sécurité pour des environnements intelligents tels que des smartphones ou des tablettes, après quoi j’aborderai les résultats d’un article récemment accepté à Tacas 2021 dans le cadre de mon postdoc portant sur la vérification quantitative de réseaux sous condition de pannes de liens. Finalement je présenterai les collaborations que j’envisage avec votre équipe, en particulier en termes de vérification modulaire d’architectures multi-protocoles mais également en termes d’utilisation de méthodes formelles pour prouver les propriétés de sécurité d’architectures distribuées multi-agents ou encore pour détecter des applications malveillantes à plusieurs niveaux d’observation.
LOVE 21/01/2021 Extensional denotational semantics of probabilistic programs, beyond the discrete case, par Guillaume Geoffroy
Guillaume Geoffroy, Università di Bologna  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
21/01/2021    10:00 - 11:00
Résumé :
The idea of extensional denotational semantics is to interpret first-order probabilistic programs as measure transformers. For example, a program that takes as input a handle to a random generator of real numbers and outputs a randomly chosen real number is interpreted as a map that takes a sub-probability measure on R and returns a sub-probability measure on R. Beyond first order, “extensional” means that each type is interpreted as a set with some additional structure, and programs as structure-preserving maps. The question of what structure exactly is a long-standing one. We will see in what way the structures that have been proposed so far are not completely satisfactory as soon as non-discrete probabilities are involved, why such a structure should at least include that of an algebra over the monad of sub-probability measures, and an example of structure that seems to fit the bill.
LOVE 14/01/2021 [Séminaire Chocola] Taylor Subsumes Scott, Berry, Kahn and Plotkin, par Giulio Manzonetto
Giulio Manzonetto, LIPN, Université Sorbonne Paris Nord  
http://chocola.ens-lyon.fr/events/seminaire-2021-01-14/
14/01/2021    10:00 - 12:00
Résumé :
The speculative ambition of replacing the old theory of program approximation based on syntactic continuity with the theory of resource consumption based on Taylor expansion and originating from the differential lambda-calculus is nowadays at hand. Using this resource sensitive theory, we provide simple proofs of important results in lambda-calculus that are usually demonstrated by exploiting Scott's continuity, Berry's stability or Kahn and Plotkin's sequentiality theory. A paradigmatic example is given by the Perpendicular Lines Lemma for the Böhm tree semantics, which is proved here simply by induction, but relying on the main properties of resource approximants: strong normalization, confluence and linearity.
LOVE 18/12/2020 On higher-order cryptography, par Raphaëlle Crubillé
Raphaëlle Crubillé, LORIA  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 749983)
18/12/2020    15:15 - 16:15
Résumé :
Type-two constructions abound in cryptography: adversaries for encryption and authentication schemes, if active, are modeled as algorithms having access to oracles, i.e. as second-order algorithms. But how about making cryptographic schemes themselves higher-order? This work gives an answer to this question, by first describing why higher-order cryptography is interesting as an object of study, then showing how the concept of probabilistic polynomial time algorithm can be generalized so as to encompass algorithms of order strictly higher than two, and finally proving some positive and negative results about the existence of higher-order cryptographic primitives, namely authentication schemes and pseudorandom functions.
LOVE 17/12/2020 History-Dependent Nominal mu-Calculus, par Clovis Eberhart
Clovis Eberhart , ERATO MMSD project, Tokyo  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
17/12/2020    10:30 - 11:30
Résumé :
The mu-calculus with atoms, or nominal mu-calculus, is a temporal logic for reasoning about transition systems that operate on data atoms coming from an infinite domain and comparable only for equality. It is, however, not expressive enough to define some properties that are of interest from the perspective of system verification. To rectify this, we extend the calculus with tests for atom freshness with respect to the global history of transitions. Since global histories can grow arbitrarily large, it is not clear whether model checking for the extended calculus is decidable. We prove that it is, by showing that one can restrict attention only to locally relevant parts of the history. This is joint work with Bartek Klin.
AOC 17/12/2020 Combinatorial Optimization problems in telecommunication networksitre bientôt disponible, par Sébastien Martin
Sébastien Martin, NTO team from DataCom Department, Huawei Technologies Co.,Ltd.  
Salle B107, bâtiment B, Université de Villetaneuse
17/12/2020    10:30 - 11:30
Résumé :
The telecommunication network area provides lot of interesting optimization problems. Furthermore, the arrival of 5G technology modifies the traditional combinatorial optimization problems by adding some specificities. We quickly present some case studies done by the "network optimization" team from "Datacom" department. For instance, we present the "network slicing technology" ensuring isolation in resource sharing among users. We also describe the "Deterministic Networking" to guarantee bounded jitter and latency constraints. Finally, we show how to consider network calculus in optimization problems to ensure latency guarantees. We finish by the presentation of future telecommunication network topics from an optimization point of view. Joint work with Nicolas Huin, Jérémie Leguay, Youcef Magnouche, Paolo Medagliani
LOVE 14/12/2020 Measurable Game Semantics, par Hugo Paquet
Hugo Paquet, University of Oxford  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 749983)
14/12/2020    10:00 - 11:00
Résumé :
I will present recent work on a denotational semantics for probabilistic programs based on games and strategies. This is a probabilistic enrichment of concurrent games on event structures, a model extensively developed in the past few years by Winskel, Clairambault, Castellan and others. Concurrent games have been used successfully to model computation with discrete probability; applications include full abstraction results for probabilistic extensions of PCF and the pure lambda-calculus. I will focus on an extension of the above with measure-theoretic structure. The resulting category supports higher-order types, continuous probability distributions, and primitives for conditioning, and can be used to model both call-by-value and call-by-name.
RCLN 07/12/2020 wikiSERA: Domain independent evaluation of automatic summaries using relevance analysis on Wikipedia, par Jorge Garcia Flores
Jorge Garcia Flores, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse
07/12/2020    12:30 - 13:30
Résumé :
Text summarization has been the subject of increasing research efforts in the last years. However, automatic summary evaluation is as crucial as the summarization task itself. For more than 15 years, the dominant approach for evaluating this task has been ROUGE [Lin, 2004], a machine translation inspired lexical comparison between a candidate machine summary and a set of human gold standard summaries. Lexical comparison might be a suitable evaluation approach for extractive summarization systems. However, the methodological leap of Deep Learning brought increasing research efforts on abstractive summarization, which raised some questions about the pertinence of an all-lexical evaluation perspective. In this work we present wikiSERA, an open source improvement of the SERA evaluation method [Cohan et al., 2018], based on a semantic comparison of information extraction vectors from a document base. We adapted the method to generic domain summarization and provide to the community a Wikipedia based implementation that shows robust correlation with human evaluations. --- Après le séminaire on va saluer Jorge qui nous quitte pour quelques mois, avec un apéro de "résistance" (contre la Covid, la LPR, etc..)
AOC 03/12/2020 Geometric Set Cover via Randomized LP Rounding, par Mustafa Nabil
Mustafa Nabil, ESIEE Paris and LIGM  
Salle B107, bâtiment B, Université de Villetaneuse
03/12/2020    10:30 - 11:30
Résumé :
Geometric set-cover/hitting-set problems arise naturally in several basic settings, and therefore the problem of computing small set covers (and hitting sets) has been studied extensively. A common first step in solving such optimization problems is to formulate and solve the corresponding covering/packing LP to get a fractional solution. Then the task reduces to constructing an integer solution from this fractional solution. In this talk, I will present a new simple iterative randomized rounding scheme that gives optimal approximation bounds, within constant factors, for many well-studied geometric systems.
AOC 26/11/2020 Émergence de nouveaux problèmes combinatoires pour les systèmes de production dans le contexte Industrie 4.0, par Paolo Gianessi
Paolo Gianessi, EMSE - Saint-Etienne  
Salle B107, bâtiment B, Université de Villetaneuse
26/11/2020    10:30 - 12:00
Résumé :
Du fait des nouveaux paradigmes de production imposés par l'Industrie 4.0 et de l'attention grandissante portée par l'opinion publique à l'égard des questions environnementales, les systèmes de production doivent relever le double défi de répondre à une demande de plus en plus variable mais aussi faire preuve d'une efficacité énergétique accrue. De nouveaux problèmes combinatoires ont ainsi commencé à paraître dans la littérature de l'Optimisation des systèmes de production à coté des problèmes plus traditionnels. Nous en présentons ici trois, que nous avons étudiés au cours de ces deux dernières années, et qui touchent à la planification stratégique ou tactique/opérationnelle: un problème d'ordonnancement de type job-shop avec prise en compte de l'énergie; un problème d'équilibrage de ligne avec minimisation du pic de puissance; et un problème bi-niveau d'équilibrage de ligne d'un RMS (système de production reconfigurable) visant à minimiser le coût de la consommation énergétique vis-à-vis d'un plan tarifaire donné. Ces problèmes ont pour l'instant été abordés par de premières approches simples (PLNE, méta-heuristiques par décomposition et/où recherche locale) afin d'en démontrer l'intérêt pratique auprès de la communauté industrielle; il paraît tout de même évident qu'ils offrent des développements potentiels à investiguer aussi d'un point de vue plus proprement algorithmique et combinatoire, et par conséquent s'affichent comme de nouveaux éléments d'intérêt certain de la frontière entre applications réelles et recherche fondamentale.
LOVE 26/11/2020 Quantitative Tauberian Theorems, par Thomas Powell
Thomas Powell, University of Bath  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
26/11/2020    10:00 - 11:00
Résumé :
In this talk I seek to achieve two things. First, I aim to give a very concise introduction to modern applied proof theory, without assuming any prior knowledge of this area. Second, I will present some new reasearch of mine in Tauberian theory, which studies the convergence of different summation methods for infinite series.
AOC 19/11/2020 A Tight Approximation Algorithm for the Cluster Vertex Deletion Problem, par Samuel Fiorini
Samuel Fiorini, Université libre de Bruxelles  
Salle B107, bâtiment B, Université de Villetaneuse
19/11/2020    10:30 - 11:30
Résumé :
We give the first 2-approximation algorithm for the cluster vertex deletion problem. This is tight, since approximating the problem within any constant factor smaller than 2 is UGC-hard. Our algorithm combines the previous approaches, based on the local ratio technique and the management of true twins, with a novel construction of a 'good' cost function on the vertices at distance at most 2 from any vertex of the input graph. As an additional contribution, we also study cluster vertex deletion from the polyhedral perspective, where we prove almost matching upper and lower bounds on how well linear programming relaxations can approximate the problem.
LOVE 19/11/2020 Introduction to Parametric Verification 2/2, par Laure Petrucci
Laure Petrucci, LIPN, Université Sorbonne Paris Nord  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
19/11/2020    10:00 - 11:00
Résumé :
(Filled in by Thomas.) The talk will be the second of two sessions providing a short introduction to parametric verification of concurrent systems. Associated ArXiv paper: https://hal.archives-ouvertes.fr/hal-02170526.
LOVE 12/11/2020 Differentiating stateful processes, par David Sprunger
David Sprunger, ERATO MMSD Project, Tokyo  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
12/11/2020    16:00 - 17:00
Résumé :
In this talk, we develop a notion of differentiation for Mealy machines with smooth transition functions. This notion of differentiation is based in the theory of Cartesian differential categories, a synthetic, categorical treatment of differentiation. We exhibit a construction augmenting any Cartesian differential category with a trace-like operation modeling internal state. We apply these categorical constructions to model recurrent neural networks, investigate compositional properties of their derivatives, and ultimately design improved training algorithms in machine learning. Joint work with Shin-ya Katsumata.
AOC 05/11/2020 An exact algorithm for robust influence maximization, par Roberto Wolfler Calvo
Roberto Wolfler Calvo, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse
05/11/2020    10:30 - 11:30
Résumé :
We propose a Branch-and-Cut algorithm for the robust influence maximization problem. The influence maximization problem aims to identify, in a social network, a set of given cardinality comprising actors that are able to influence the maximum number of other actors. We assume that the social network is given in the form of a graph with node thresholds to indicate the resistance of an actor to influence, and arc weights to represent the strength of the influence between two actors. In the robust version of the problem that we study, the node thresholds are affected by uncertainty and we optimize over a worst-case scenario within a given robustness budget. Numerical experiments show that we are able to solve to optimality instances of size comparable to other exact approaches in the literature for the non-robust problem, but in addition to this we can also tackle the robust version with similar performance.
LOVE 05/11/2020 Journée Opérades LIPN-LAGA, par Conférence
Conférence  
https://operades20.sciencesconf.org
05/11/2020    09:30 - 16:00
Résumé :
Le programme est disponible en ligne (https://operades20.sciencesconf.org). Pensez à vous inscrire sur le site pour recevoir les informations de connexion. Le premier exposé contiendra une introduction à la théorie des opérades. Liste des orateurs invités: Samuele Giraudo (LIGM, U. Gustave Eiffel), Guillaume Laplante-Anfossi (LAGA, U. Sorbonne Paris Nord), Maxime Lucas (LIPN, U. Sorbonne Paris Nord), Damiano Mazza (LIPN, CNRS).
LOVE 29/10/2020 Mathematical specifications of programming languages via modules over monads, par Ambroise Lafont
Ambroise Lafont, Cogent team, University of New South Wales  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 749983)
29/10/2020    09:00 - 10:00
Résumé :
Research in the field of programming languages traditionally relies on a definition of syntax modulo renaming of bound variables, with its associated operational semantics. We are interested in mathematical tools allowing us to automatically generate syntax and semantics from basic data. We pay particular attention to the notion of substitution, using the categorical notions of monads and modules over them. Languages with variable binding, such as the pure lambda calculus, are monads on the category of sets. We provide a further notion of transition monads which takes into account the operational semantics. We give examples of specifications for transition monads, in the spirit of Initial Semantics, where an object is characterized by some initiality property in a suitable category of models.
LOVE 22/10/2020 Introduction to Parametric Verification 1/2, par Laure Petrucci
Laure Petrucci, LIPN, Université Sorbonne Paris Nord  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
22/10/2020    10:00 - 11:00
Résumé :
(Filled in by Thomas.) The talk will be the first of two sessions providing a short introduction to parametric verification of concurrent systems. Associated ArXiv paper: https://hal.archives-ouvertes.fr/hal-02170526.
LOVE 15/10/2020 Interaction Laws of Monads and Comonads, par Exequiel Rivas
Exequiel Rivas, Inria  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
15/10/2020    10:00 - 11:00
Résumé :
Since Moggi's seminal work, monads have been recognized as a way of capturing computational effects. Following this line, we take a view in which their dual, comonads, can be used to capture some form of environment that can interact with such computations. In this talk, we will present a categorical theory of interaction between monads and comonads, abstracting the execution of a computation in an environment. We will highlight connections to previous categorical constructions such as the Chu construction and gluing in the style of Hasegawa. This is joint work with Shin-ya Katsumata and Tarmo Uustalu.
RCLN 12/10/2020 Person-Independent Multimodal Emotion Detection for Children with High-Functioning Autism, par Annanda Sousa
Annanda Sousa, Université de Galway (Irlande)  
Salle B107, bâtiment B, Université de Villetaneuse
12/10/2020    12:30 - 14:00
Résumé :
The use of affect-sensitive interfaces carries the promise of enhancing human-computer interaction by delivering a system capable of identifying a user's emotions and adapt its content accordingly. Today's technology shows great potential to support children with autism, for example by using computer systems to improve their social skills. Generally, however, this technology does not encompass the potential of affect-sensitive interfaces. This is mainly due to Emotion Detection (ED) models built for the general population usually not performing well when applied to children with autism, who express emotions differently. The aim of this project is therefore to build a person-independent Multimodal Emotion Detection system tailored for children with high-functioning autism for the ultimate goal of applying it to design affect-sensitive interfaces dedicated to children with autism. This is a work in progress and the project expects to build upon the current body of knowledge on methods to apply ED systems to this specific subset of the general population. We expect to apply the overall theoretical and practical design perspectives that arise from this research investigation (e.g. analysis of modalities and features extraction, behavioural cues based features, fusion layers and classifier techniques) to propose a guiding framework for future studies.
LOVE 08/10/2020 On Higher-Order (In)Efficiencies, par Gabriele Vanoni
Gabriele Vanoni, Università di Bologna  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
08/10/2020    10:00 - 11:00
Résumé :
Intersection types (IT) for the lambda-calculus extend simple types with an intersection operator. They are able to characterize crucial qualitative properties of programs, such as strong, weak and head normalization, and they have been extensively studied for their connections with models and semantics of programming languages. Moreover, considering a variation of the type system in which the intersection is non-idempotent, has led to new quantitative results and simplified many proofs, in the very same way linear logic did, i.e. taking into account the use of resources. This way, non-idempotent IT are able to characterize, for example, the number of steps Krivine’s machine needs to evaluate a term. We show how altering the way in which weights are assigned gives the number of steps the Interaction Abstract Machine (IAM) needs to evaluate a term. This way, we quantitatively observe that the inefficiencies of the IAM come from the presence of higher-order types in the IT derivation. This is joint work with Beniamino Accattoli and Ugo Dal Lago.
LOVE 01/10/2020 Cons-free programs for functional complexity classes, par Siddharth Bhaskar
Siddharth Bhaskar, DIKU, University of Copenhagen  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
01/10/2020    10:00 - 11:00
Résumé :
The "cons-free programs" of Neil Jones, in which data can be destructed but not constructed, capture relational LOGSPACE or PTIME over strings, depending on whether we allow tail recursion or general recursion. By generalizing cons-free programs to "RW-factorizable programs," in which there are separate construct-only and destruct-only data types, we recover functional LOGSPACE and PTIME over strings. This seems to be a novel implicit characterization of these classes. RW-factorizable programs faithfully express several natural algorithms. In particular, we study RW-factorizable comparison sorting, prove a quadratic lower bound on the running time of all such sorting programs, and show that this is tight. Finally we conclude with some thoughts about a program for "comparative implicit computational complexity," based on studying indexings of complexity classes obtained from various implicit characterizations.
RCLN 28/09/2020 Recherche d’experts à partir de publications scientifiques, par Stella Zevio
Stella Zevio, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse
28/09/2020    12:30 - 13:30
Résumé :
Qui assigner au comité de lecture de la conférence que j'organise ? Au comité de thèse de mon doctorant ? Qui sont les membres éminents et les publications phares de mon domaine de recherche ? Suis-je un chercheur émérite ? Qui dois-je citer et avec qui dois-je collaborer pour espérer faire partie des membres éminents de la communauté scientifique et améliorer ma réputation ? Afin de répondre à ces problématiques essentielles, nous proposons une méthode de recherche d’experts à partir de publications scientifiques combinant annotation sémantique à l’aide d’une ontologie et fouille de motifs dans les coeurs de graphes attribués.
LOVE 24/09/2020 Intersection Type Distributors, par Federico Olimpieri
Federico Olimpieri, Aix-Marseille Université  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
24/09/2020    10:00 - 11:00
Résumé :
Building on previous works, we present a general method to define proof relevant intersection type semantics for pure lambda calculus. We argue that the bicategory of distributors is an appropriate categorical framework for this kind of semantics. We first introduce a class of 2-monads whose algebras are monoidal categories modelling resource management, following Marsden-Zwardt's approach. We show how these monadic constructions determine Kleisli bicategories over the bicategory of distributors and we give a sufficient condition for cartesian closedness. We define a family of non-extentional models for pure lambda calculus. We then prove that the interpretation of lambda terms induced by these models can be concretely described via intersection type systems. The intersection constructor corresponds to the particular tensor product given by the considered free monadic construction.
LOVE 17/09/2020 All your base categories are belong to us: A syntactic model of presheaves in type theory, par Pierre-Marie Pédrot
Pierre-Marie Pédrot, INRIA  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (code d'accès: 749983)
17/09/2020    10:00 - 11:00
Résumé :
Presheaves are a staple categorical structure, which naturally arises in a wide variety of situations. In the realm of logic, they are often used as a model factory. Indeed, presheaves over some base category will result in a topos, whose contents can be fine-tuned by carefully picking the base category. As computer scientists, though, we have learnt that there are even better logical systems than toposes: dependent type theories! Through the Curry-Howard mirror, they are also full-blown functional programming languages that actually compute. This begs the following question: is it possible to build the type-theoretic equivalent of presheaves, while retaining the good computational properties of our dependent programming languages? We will see that strikingly enough, presheaves can already be presented as computational objects to some extent, except for the annoying fact that they do not obey the right conversion rules! A proper account of type-theoretic presheaves will require a coming-of-age journey through the world of effectful program semantics, using fine and modern tools such as call-by-push-value, dependent parametricity and strict equality. In the end, we will formulate an alternative presentation of presheaves in type theory, but which is still equivalent to its standard categorical counterpart when viewed from the static world of sets. As an application, we will use them to extend dependent type theory with new effective logical principles.
LOVE 18/06/2020 SSAFire, a Monadic Gated SSA representation and its optimizations, par Thomas Rubiano
Thomas Rubiano, INRIA  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24
18/06/2020    10:00 - 11:30
Résumé :
I'll present SSAFire, a variant of the monadic gated Static Single Assignment form, where programs are represented by dependency graphs, rather than control-flow graphs. Its referential transparency makes it useful to implement several global program optimizations as simple graph transformations that can be justified using symbolic and local reasoning.
LOVE 11/06/2020 Exploiting Pointer Analysis in Memory Models for Deductive Verification, par Mihaela Sighireanu
Mihaela Sighireanu, University Paris Diderot, IRIF  
https://bbb.lipn.univ-paris13.fr/b/ari-uht-t3u
11/06/2020    14:00 - 15:00
Résumé :
Cooperation between verification methods is crucial to tackle the challenging problem of software verification. I'll present such a collaboration involving static analyzers doing pointer analysis and a deductive verification method based on first order logic. The idea is to exploit the result of pointer analysis in order to provide a memory model to the deductive verification that captures precisely the disjointedness of regions in the program memory. The accuracy obtained in the memory model is essential for shortening aliasing annotations and improve the results of automated solvers. This cooperation has been implemented inside the Frama-C platform.
RCLN 08/06/2020 Generating Referring Expressions from RDF Knowledge Graphs for Data Linking , par Armita Khajeh-Nassiri
Armita Khajeh-Nassiri  
Virtuel sur Jitsi: https://jitsi.lipn.univ-paris13.fr/RDFKGforDataLinking
08/06/2020    15:00 - 16:00
Résumé :
In a knowledge graph, a referring [removed]RE) is a logical formula that can uniquely identify an entity. We propose a novel approach for discovering REs that are valid within a class of a knowledge graph. There can potentially exist many REs for each entity, hence we have focused on those descriptions that are 1) minimal 2) diverse and that 3) can not be found by instantiating the keys. As an application, we study the data linking problem that, given two knowledge graphs G1 and G2, finds the possible links between the entities of G1 and G2. We show that REs can drastically improve the quality of data linking. Rejoindre la réunion?: https://jitsi.lipn.univ-paris13.fr/RDFKGforDataLinking
LOVE 04/06/2020 Logic Beyond Formulas: A Proof System on Graphs, par Matteo Acclavio
Matteo Acclavio, SaToSS, Université du Luxembourg  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 638888)
04/06/2020    10:00 - 11:30
Résumé :
In proof theory, proof systems usually operate on formulas, that is, objects characterized by an underlying tree structure. The aim of this talk is to define a proof system operating on general (undirected) graphs instead of formulas. We start from the correspondence between formulas and cographs, i.e. graphs containing no chordless paths of length 3. As a consequence of considering general graphs, we can no longer use the standard proof theoretical methods relying on the tree structure of formulas: for instance, we are not able to identify the main connective of a formula. Thanks to graphs modular decomposition and some techniques from deep inference, we are able to define a proof system with admissible cut and which is a conservative extension of MLL with mix. This talk is based on a joint work with Ross Horne and Lutz Strassburger.
LOVE 28/05/2020 A cellular Howe theorem, par Tom Hirschowitz
Tom Hirschowitz, CNRS & Université Savoie Mont Blanc  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 638888)
28/05/2020    11:00 - 12:30
Résumé :
We introduce a categorical framework for operational semantics, in which we define substitution-closed bisimilarity, an abstract analogue of the open extension of Abramsky's applicative bisimilarity. We furthermore prove a congruence theorem for substitution-closed bisimilarity, following Howe's method. We finally demonstrate that the framework covers the call-by-name and call-by-value variants of lambda-calculus in big-step style. As an intermediate result, we generalise the standard framework of Fiore et al. for syntax with variable binding to the skew-monoidal case. This is joint work with Peio Borthelle and Ambroise Lafont.
LOVE 19/05/2020 Focusing on lambda-calculus equivalence, par Gabriel Scherer
Gabriel Scherer, INRIA  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 638888)
19/05/2020    15:30 - 17:00
Résumé :
In this overview talk we will show how the logical technique of focusing can be applied to better understand program equivalence in the simply-typed lambda-calculus with datatypes (in particular sums and the empty type). The talk will not assume familiarity with focusing, and introduce it in the context of propositional intuitionistic logic. We will then present a focused presentation of the (normal forms of the) lambda-calculus. If time allow, we will then introduce the "saturated" normal forms, a stronger restriction that we used in https://arxiv.org/abs/1610.01213 (2017) to decide equivalence of simply-typed lambda-terms with sums and the empty type.
LOVE 07/05/2020 Implicit automata in typed lambda-calculi, par Nguyen Lê Thành Dung
Nguyen Lê Thành Dung, LIPN, Université Sorbonne Paris Nord  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 638888)
07/05/2020    10:00 - 11:30
Résumé :
We show that various classes of languages and functions from automata theory can be equivalently defined using lambda-calculi with substructural types. For instance, we characterize regular string-to-string functions with affine types, and star-free languages with non-commutative types. These results have few direct precedents, but they are analogous to the field of implicit computational complexity, except with automata instead of complexity classes. Our starting point is the little-known fact that the predicates definable over Church-encoded strings in the simply typed lambda-calculus are exactly the regular languages (Hillebrand & Kanellakis, LICS'96). More recently, similar ideas have played a prominent role in higher-order model checking. This is joint work with Pierre Pradic (University of Oxford).
LOVE 30/04/2020 Taylor Subsumes Scott, Berry, Kahn and Plotkin, par Davide Barbarossa
Davide Barbarossa, LIPN  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 638888)
30/04/2020    10:00 - 11:30
Résumé :
The speculative ambition of replacing the old theory of program approximation based on syntactic continuity with the theory of resource consumption based on Taylor expansion and originating from the differential lambda-calculus is nowadays at hand. Using this resource sensitive theory, we provide simple proofs of important results in lambda-calculus that are usually demonstrated by exploiting Scott's continuity, Berry's stability or Kahn and Plotkin's sequentiality theory. A paradigmatic example is given by the Perpendicular Lines Lemma for the Böhm tree semantics, which is proved here simply by induction, but relying on the main properties of resource approximants: strong normalization, confluence and linearity.
AOC 23/04/2020 Méthodes primal-dual avec la programmation linéaire des configurations, par Nguyen Kim Thang
Nguyen Kim Thang, Université d'Evry  
Salle B107, bâtiment B, Université de Villetaneuse
23/04/2020    10:30 - 11:30
Résumé :
Primal-duale est une méthode élégante et puissante en optimisation et en algorithmique. La méthode consiste à établir de manière interactive des solutions primals et duales, puis un algorithme, ainsi que son analyse, sont guidés naturellement par l'interaction primal-duale. Dans cet exposé, je vais présenter les approches primal-dual comme techniques unifiées afin d'étudier et de développer les algorithmes les domaines de la théorie des jeux algorithmiques et de l'algorithmique en ligne.
LOVE 23/04/2020 The Complexity of Interaction Abstract Machines, par Gabriele Vanoni
Gabriele Vanoni, Università di Bologna  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 638888)
23/04/2020    10:00 - 11:30
Résumé :
Geometry of Interaction (GOI) is a semantic framework describing the dynamics of cut-elimination in the Multiplicative Exponential fragment of Linear Logic (MELL). It has been formulated in many ways, from operator algebras to traced symmetrical monoidal categories. Remarkably, some of these formulations, in particular Context Semantics by Gonthier et al. led to the introduction of compilation techniques (Mackie '95) and abstract machines for higher-order functional languages (Danos and Regnier '99). However, these machines were always based on a proof-net representation of programs, via the so-called Girard translation. We introduce an abstract machine in the spirit of GOI based directly on the ?-calculus, without any explicit use of proof-nets. We prove soundness and adequacy, and we derive in our framework an optimization already presented by Danos and Regnier. We complete our study with a complexity analysis of those machines.
A3 16/04/2020 Décomposition et recherche Monte Carlo en General Game Playing, par Nicolas Jouandeau
Nicolas Jouandeau, Université Paris 8  
Salle B107, bâtiment B, Université de Villetaneuse
16/04/2020    12:15 - 13:45
Résumé :
Les jeux permettent de définir des problèmes non triviaux dans un cadre fini et maîtrisé, et offrent de fait un cadre intéressant pour l’étude des algorithmes de décision. Pour réduire l'influence de connaissances expertes spécifiques à un jeu et stimuler une analyse logique des problèmes, le General Game Playing (GGP) propose de jouer à des jeux inconnus en partant uniquement de la description logique de leurs règles. Dans ce contexte, nous proposons deux méthodes générales de décomposition des jeux décrits en Game Description Language (GDL), l'une s’appuyant sur une analyse logique des règles et l'autre sur une analyse statistique d’informations collectées pendant des simulations. Enfin nous présentons une variation de la méthode Monte Carlo Tree Search exploitant ces décompositions dans un joueur GGP et permettant de résoudre simplement certains jeux.
LOVE 16/04/2020 Automatic Differentiation in PCF, par Damiano Mazza
Damiano Mazza, LIPN, CNRS & Université Paris 13  
https://bbb.lipn.univ-paris13.fr/b/sei-eer-t24 (access code: 638888)
16/04/2020    10:00 - 11:00
Résumé :
Automatic differentiation (AD) is the science of efficiently computing the derivative (or gradient, or Jacobian) of functions specified by computer programs. It is a fundamental tool in several fields, most notably machine learning, where it is the key for training deep neural networks. Albeit AD techniques traditionally focus on a restricted class of programs, namely first-order straight-line programs, the rise of so-called differentiable programming in recent years has called for the need of applying AD to complex code, containing all sorts of control flow operators and higher-order combinators. In this talk, I will discuss the extension of AD algorithms to PCF, a(n idealized) purely functional programming language. We will first consider the simply-typed lambda-calculus, showing in particular how linear negation is related to reverse mode AD (aka backpropagation), and then see how the extra features of PCF, namely full recursion and conditionals, may be dealt with, stressing the difficulties posed by the latter. [Joint work with Aloïs Brunel (Deepomatic) and Michele Pagani (IRIF, Université de Paris)]
AOC 26/03/2020 Multi-period Hub Location Problem with Serial Demands: A Case Study of Humanitarian Aids Distribution in Lebanon, par Shahin Gelareh
Shahin Gelareh, Université d’Artois  
Salle B107, bâtiment B, Université de Villetaneuse
26/03/2020    10:30 - 11:30
Résumé :
We address the problem of humanitarian aids distribution across refugee camps in war-ridden areas from a network design perspective. We show that the problem can be modeled as a variant of multi-period hub location problem with a particular demand pattern resulted by the user's behavior. The problem has been motivated by a case study of Lebanese experience in Syrian war refugee accommodation. We elaborate on the complexity and real-life constraints and, propose a compact formulation of a mathematical model of the problem. We then show that modeling the problem using a Benders paradigm drives O(n^3) variables of the original compact model unnecessary in addition to the constraints that are being projected out in a typical Benders decomposition. Additionally, we identify several classes of valid inequalities together with efficient separation procedures leading to a cut-and-Benders approach. Our extensive computational experiments on the case study with real data as well as randomly generated instances proves the performance of proposed solution methods.
LOVE 19/03/2020 REASONING ABOUT DYNAMIC NETWORKS OF INFINITE-STATE PROCESSES , par Mihaela Sighireanu
Mihaela Sighireanu , University Paris Diderot, IRIF  
Salle A303, Institut Galilée, Université Sorbonne Paris Nord
19/03/2020    10:00 - 11:00
Résumé :
We propose a framework for reasoning about unbounded dynamic networks of infinite-state processes. We propose Constrained Petri Nets (CPN) as generic models for these networks. They can be seen as Petri nets where tokens (representing occurrences of processes) are colored by values over some potentially infinite data domain such as integers, reals, etc. Furthermore, we define a logic, called CML (colored markings logic), for the description of CPN configurations. CML is a first-order logic over tokens allowing to reason about their locations and their colors. Both CPNs and CML are parametrized by a color logic allowing to express constraints on the colors (data) associated with tokens. We investigate the decidability of the satisfiability problem of CML and its applications in the verification of CPNs. We identify a fragment of CML for which the satisfiability problem is decidable (whenever it is the case for the underlying color logic), and which is closed under the computations of post and pre images for CPNs. These results can be used for several kinds of analysis such as invariance checking, pre-post condition reasoning, and bounded reachability analysis.
A3 16/03/2020 What (many kinds of) graphs can contribute to explainable machine learning, par Tiphaine Viard
Tiphaine Viard, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse
16/03/2020    12:15 - 13:45
Résumé :
AI and machine learning are commonly described as "black boxes" that are efficient, but opaque. While complete opacity would be an exaggeration, it is true that many methods for explainability rely on forms of retro-engineering: we try to infer the model from its (partial, intermediary, final) results. These methods are typically based on large-scale, efficient matrix manipulation. Graphs and their extensions have shown to be visualisable and interpretable, even at large scales. In their classical formulation, they are also very similar to matrices, but also versatile: they can be directed, weighted, multilayered, temporal, etc. Each of those extensions giving rise to interesting algorithmic and data-driven questions. To date, few machine learning methods, harness the expressive power of graphs, in part due to the complexities of graph algorithms, typically having polynomial running times, which is incompatible with the scale of data at hand. However, the situation has changed: (i) the impact of AI on society makes it no longer acceptable to only favour efficiency despite explainability, and (ii) recent advances in algorithmic methods on graphs demonstrates that due to the nature of real-world graphs, even some NP-hard problems become tractable. The aim of this talk is to explore this avenue of research. We will discuss the state-of-the art as well as some past results in real-world (temporal) graph modeling and in explainability, and will then discuss some recent results on pattern mining on temporal graphs.
RCLN 10/02/2020 Attention is all I need, par José Angel Gonzalez-Barba
José Angel Gonzalez-Barba, Universidad Politécnica de Valencia  
Salle B107, bâtiment B, Université de Villetaneuse
10/02/2020    12:30 - 13:30
Document attaché
Résumé :
The use of attention mechanisms has been widespreaded along all the natural language processing tasks. These kind of mechanisms have increased the capacity of Deep Learning models allowing them to focus explicitly on the most discriminant relationships and properties for a given task. Recently, the Transformer model have replaced Convolutional and Recurrent neural networks in many NLP tasks, mainly due to its capability of modeling sequences, avoiding the sequential processing by using only attention mechanisms. In this talk I will speak about the application of the Transformer encoders to text classification in social media (Sentiment Analysis and Irony Detection in Twitter) and its application in a novel framework for extractive summarization. About the author: José Angel just finished his PhD and he is going to start a PostDoc in the group of Yoshua Bengio at the University of Montreal. His works on Spanish NLP have been very promising and he developed some state-of-the-art systems for sentiment analysis and summarization.
LOVE 30/01/2020 On the Versatility of Open Logical Relations: Continuity, Automatic Differentiation, and a Containment Theorem, par Raphaëlle Crubillé
Raphaëlle Crubillé, IMDEA  
Salle B107, bâtiment B, Université de Villetaneuse
30/01/2020    10:15 - 12:00
Résumé :
I will present a joint work with Barthe, Dal Lago and Gavazzo. Logical relations are one of the most powerful techniques in the theory of programming languages, and have been used exten- sively for proving properties of a variety of higher-order calculi. However, there are properties that cannot be immediately proved by means of log- ical relations, for instance program continuity and differentiability in higher-order languages extended with real-valued functions. Informally, the problem stems from the fact that these properties are naturally ex- pressed on terms of non-ground type (or, equivalently, on open terms of base type), and there is no apparent good definition for a base case (i.e. for closed terms of ground types). To overcome this issue, we introduce a generalization of the concept of a logical relation, which we dub open logi- cal relation, and prove that it can be fruitfully applied in several contexts in which the property of interest is about expressions of first-order type. Our setting is a simply-typed ?-calculus enriched with real numbers and real-valued first-order functions from a given set, such as the one of con- tinuous or differentiable functions. We first prove a containment theorem stating that for any such a collection of functions including projection functions and closed under function composition, any well-typed term of first-order type denotes a function belonging to that collection. Then, we show by way of open logical relations the correctness of the core of a recently published algorithm for forward automatic differentiation. Fi- nally, we define a refinement-based type system for local continuity in an extension of our calculus with conditionals, and prove the soundness of the type system using open logical relations.
LOVE 20/12/2019 Parametric schedulability analysis of a launcher flight control system under reactivity constraints, par Jawher Jerray
Jawher Jerray, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse
20/12/2019    15:00 - 15:30
Résumé :
The next generation of space systems will have to achieve more and more complex missions. In order to master the development cost and duration of such systems, an alternative to a manual design is to automatically synthesize the main parameters of the system. In this work, we present an approach on the specific case of the scheduling of the flight control of a space launcher. The approach requires two successive steps: (1) the formalization of the problem to be solved in a parametric formal model and (2) the synthesis of the model parameters with a tool in an optimal way. We first describe the problematic of the scheduling of a launcher flight control, then we show how this problematic can be formalized with parametric stopwatch automata; we then present the results computed by IMITATOR. We compare the results to the ones obtained by other tools classically used in scheduling.
LOVE 20/12/2019 Concurrent Algorithms and Data Structures for Model Checking, par Jaco van de Pol
Jaco van de Pol, Aarhus University  
Salle B107, bâtiment B, Université de Villetaneuse
20/12/2019    14:00 - 15:00
Résumé :
Model checking is a successful method for checking properties on the state space of concurrent, reactive systems. Since it is based on exhaustive search, scaling the method to industrial systems has been a challenge since its conception. Research has focused on clever data structures and algorithms, to reduce the size of the state space or its representation; smart search heuristics, to reveal potential bugs and counterexamples early; and high-performance computing, to deploy the brute force processing power of clusters of compute-servers. The main challenge is to combine a brute force approach with clever algorithms: brute force alone (when implemented carefully) can bring a linear speedup in the number of processors. This is great, since it reduces model-checking times from days to minutes. On the other hand, proper algorithms and data structures can lead to exponential gains. Therefore, the parallelization bonus is only real if we manage to speedup clever algorithms. There are some obstacles: many linear-time graph algorithms depend on a depth-first exploration order, which is hard to parallelize. Examples include the detection of strongly connected components (SCC), and the nested depth-first-search (NDFS) algorithm. Both are used in model checking LTL properties. Symbolic representations, like binary decision diagrams (BDDs), reduce model checking to "pointer-chasing", leading to irregular memory-access patterns. This poses severe challenges on achieving actual speedup in (clusters of) modern multi-core computer architectures. This talk will present some of the solutions found over the last 10 years, leading to the high-performance model checker LTSmin. These include parallel NDFS (based on the PhD thesis of Alfons Laarman), the parallel detection of SCCs with concurrent Union-Find (based on the PhD thesis of Vincent Bloemen), and concurrent BDDs and other decision diagrams (based on the PhD thesis of Tom van Dijk). This functionality is provided in a specification-language agnostic manner, while exploiting the locality typical for a-synchronous distributed systems (based on the PhD thesis of Jeroen Meijer). Finally, I will sketch a perspective on moving forward from high-performance model checking to high-performance synthesis algorithms. Examples include parameter synthesis for stochastic and timed systems, and strategy synthesis for (stochastic and timed) games. The focus of the talk will be on a parallel algorithm for SCC decomposition
LOVE 17/12/2019 Parallel verification of concurrent systems using the Symbolic Observation Graph, par Hiba OUNI
Hiba OUNI, LIPN  
Salle A303
17/12/2019    12:30 - 13:30
Résumé :
Model checking is one of the major techniques used in formal verification. This technique takes a model of a system in question and decides whether it satisfies a given property or not. It is based on an exhaustive exploration of the state space of the system to be verified. Thus, the Model checking technique suffers from the state space explosion problem: it can happen that the verification process stops because of lack of time or space. One of the proposed solutions to tackle this problem is to parallelize the verification process. The use of distributed processing increases the speedup and scalability of model checking by exploiting the cumulative computational power and memory of a cluster of computers. Such approaches have been studied in various contexts leading to different proposed solutions for both symbolic and explicit model checking. In this talk, we shall present new model checking algorithms built on a parallel construction of the Symbolic Observation Graph: an abstraction of the state space graph that preserves Linear Temporal Logic (LTL). We implemented the proposed model checking algorithm within a C++ prototype and compared our preliminary results with the state of the art model checkers.
LOVE 14/11/2019 Formal Specification and Verification of Interactive Multimedia Scores, par Jaime Arias
Jaime Arias, LIPN  
Salle A303
14/11/2019    13:00 - 14:00
Résumé :
Interactive Scores (IS) is a formalism for composing and performing interactive multimedia scores with several applications in video games, live performance installations, and virtual museums. In this model, the composer defines the temporal organization of the score by asserting temporal relations (TRs) between temporal objects (TOs). At execution time, the performer may modify the start/stop times of the TOs by triggering interaction points while the system guarantees that all the TRs are satisfied. Implementations of IS and formal models of their behavior have already been proposed, but these do not provide usable means to reason about their properties. In this talk we presente a Timed Automata model that fully captures the temporal structure of IS during both composition and execution, and that makes it possible to reason about the written scores.
LOVE 07/11/2019 Journee CoGITARe, par Divers
Divers  
Salle B107, bâtiment B, Université de Villetaneuse
07/11/2019    10:00 - 17:00
Résumé :
Quatre exposés autour de l'inférence de types pour divers systèmes avec intersection et union. Exposants : Stephen Dolan, Giuseppe Castagna, Claude Stolze et Flavien Breuvart programme : https://lipn.univ-paris13.fr/~breuvart/CoGITARe/journee_inferencing_subtypes.php?lang=uk
LOVE 24/10/2019 Relative monads for relational reasoning, par Kenji Maillard
Kenji Maillard, Inria Paris  
Salle B107, bâtiment B, Université de Villetaneuse
24/10/2019    10:15 - 12:00
Résumé :
Relational verification is concerned with the problem of proving specifications relating either two runs of a single program, such as non-interference, or two different programs, for instance simulations or equivalences. Starting with Benton's Relational Hoare Logic for imperative programs, many varieties of relational program logics have been designed for specific classes of relational properties and effects. Focusing on the setting of monadic computations, we want to design a generic framework for relational program logics. In our quest to understand the federating principles underlying relational reasoning, we explain how basic core properties of relational program logics are suitably captured by relative monads, a generalization of monads that need not to be an endofunctor. Working "over the product", these relative monads establish a bridge between two computational monads, employed to encapsulate their relational specifications.
A3 17/10/2019 Explicative Data Analytics, par Martin Atzmüller
Martin Atzmüller, Tilburg University  
Salle B107, bâtiment B, Université de Villetaneuse
17/10/2019    14:00 - 16:00
Résumé :
Modeling and mining multi-modal and heterogeneous data is important in the context of analyzing knowledge and information processes in complex environments, e.g. for mining high dimensional and heterogeneous (sensor) data, the analysis of exceptional patterns, and complex network structures. For making sense of the data, explicative data analytics focuses on interpretable, transparent and explainable approaches, which is relevant for very many applications for analyzing data in science and industry. The talk presents according approaches for explicative data analytics incorporating methods from data science, machine learning, and human computing, exemplified by multi-modal sensor data analysis, pattern mining and graph analytics.
A3 03/10/2019 Optimal Transport for Machine Learning, par Bernard Kamsu-Foguem
Bernard Kamsu-Foguem, ENIT, Tarbes  
Salle B107, bâtiment B, Université de Villetaneuse
03/10/2019    12:15 - 13:45
Résumé :
Optimal transport defines a set of geometric tools with interesting properties (comparison and morphology of probability measurements) that make it particularly suitable for solving large scale artificial learning problems. Since probability distributions are omnipresent in Machine Learning (ML), whether theoretical or empirical, optimal transport can be useful in order to measure their separation or, even better, to be able to transform them at a lower cost. We will investigate techniques based on optimal transport in certain practical and theoretical contexts (text classification, multi-label classification and domain adaptation), to contribute to solving the associated Machine Learning (ML) problems.
RCLN 30/09/2019 Détection de la radicalisation sur les réseaux sociaux, par Frédérique Segond
Frédérique Segond, Inalco  
Salle C316
30/09/2019    12:30 - 13:30
Résumé :
Dans ce séminaire je présenterai le travail effectué dans le cadre du projet européen Saffron pour détecter la radicalisation sur les réseaux sociaux. Après avoir présenté la problématique et l’approche multidisciplinaire adoptée, je me focaliserai sur la description des modules d’analyse sémantique, en particulier sur le module d’extraction d’événements. J’illustrerai mon propos avec les difficultés rencontrées et parlerai de la difficulté d’évaluer un tel travail. Je conclurai en présentant les perspectives actuelles de ce travail par rapport à des projets en cours et à la plateforme MediaCentric développée chez Bertin IT.
MERCRED 25/09/2019 Brzozowski and Antimirov reordering derivatives, par Tarmo Uustalu
Tarmo Uustalu, Reykjavik / Tallinn  
Salle B107, bâtiment B, Université de Villetaneuse
25/09/2019    14:00 - 15:00
Résumé :
The Brzozowski and Antimirov derivatives are effective operations on regular expressions that calculate the (semantic) derivatives of a regular language. They yield constructions of finite deterministic and nondeterministic automata. In this talk, I show how these operations on regular expressions admit natural generalizations for trace closures of regular languages, which are languages obtained from a regular language by allowing some pairs of letters to commute. The automata from the Brzozowski and Antimirov reordering derivatives are generally not finite. But if the regular expression is star-connected or, more generally, if its language has uniform rank, they are. This is joint work with Hendrik Maarand. I will also give a short introduction to what we do in my groups in Tallinn and Reykjavik.
AOC 24/09/2019 Quelques problèmes d'optimisation dans les réseaux, par Cedric Bentz
Cedric Bentz, CNAM  
Salle B107, bâtiment B, Université de Villetaneuse
24/09/2019    12:30 - 13:30
Résumé :
J'évoquerai dans cet exposé quelques problèmes d'optimisation dans les réseaux auxquels je me suis intéressé, parfois en collaboration avec d'autres chercheurs, depuis quelques années. Dans certaines des variantes étudiées, les réseaux considérés peuvent être sujets aux pannes, ce qui peut nécessiter d'en tenir compte lors de la conception de tels réseaux. La première famille de problèmes étudiés tourne autour de généralisations du problème de multicoupe, prenant notamment en compte le fait que le bon fonctionnement d'un réseau peut être mis en cause même si seul un certain nombre des communications à assurer sont affectées, pour lesquelles des résultats de complexité paramétrée ont été récemment obtenus dans différents cas particuliers. La seconde famille tourne autour de problèmes de d-bloqueurs dans les graphes, dans lesquels on s'intéresse au nombre minimum de noeuds (sommets) ou de liens (arêtes) qui doivent tomber en panne pour que, intuitivement, le réseau descende en-dessous d'un certain seuil de fonctionnement. Plusieurs résultats de complexité notables ont ainsi été obtenus pour cette catégorie de problèmes, dont on ne sait souvent même pas déterminer facilement s'ils sont dans NP ou non. Enfin, la troisième et dernière famille tourne autour de problèmes d'arbres et de réseaux de Steiner, en présence de capacités, et dans certains cas de pannes. Concernant le problème d'arbre de Steiner avec capacités sur les arcs mais sans pannes, les résultats de complexité qui ont été obtenus permettent d'obtenir une caractérisation complète de la complexité de ce problème vis-à-vis de plusieurs paramètres. Concernant le problème de conception de réseaux de Steiner avec capacités et pannes, plusieurs formulations le modélisant, dont une formulation biniveau, ont été obtenues et comparées entre elles, de façon théorique comme expérimentale, et quelques inégalités permettant de les renforcer ont également été testées. Ces formulations peuvent toutes être adaptées au cas où l'on ajoute la possibilité de protéger un certain nombre de liens du réseau, mais un fait notable et pas nécessairement intuitif est que les relations entre les formulations diffèrent alors du cas précédent.
LOVE 19/09/2019 Unifying abstract and linear rewriting. , par Maxime
Maxime, Lucas  
Salle B107, bâtiment B, Université de Villetaneuse
19/09/2019    10:00 - 11:30
Résumé :
As opposed to abstract rewriting (where one studies a set of term up to some rewrite rules), linear rewriting consists in studying linear combinations of terms, up to some rewrite rules. However the naive definitions of termination does not work in this case. The usual solution consists in only considering well-formed rewriting steps. This however is not very satisfactory because usual rewriting lemmas cannot be applied directly to the linear case and have to be proven again. In this talk we present a formalism unifying the abstract and linear cases, based on the notion of reduction strategy. In this setting, we recover an analogue of Newman's Lemma, while weakening the termination hypothesis.
AOC 17/09/2019 Algorithmes auto-stabilisants, par Lélia Blin
Lélia Blin, Sorbonne Université LIP6  
Salle B107, bâtiment B, Université de Villetaneuse
17/09/2019    12:30 - 13:30
Résumé :
Dans le contexte des réseaux à grande échelle, la prise en compte des pannes est une nécessité. L'auto-stabilisation est une approche algorithmique de la tolérance aux pannes dans les systèmes distribués dont le but est de gérer la corruption de la mémoire des processeurs dues à des pannes transitoires. Plusieurs paramètres caractérisent l'efficacité d'un algorithme auto-stabilisant, dont en particulier (1) le temps pris par le système pour retourner dans une configuration légale suite à une corruption arbitraire de la mémoire de ses processeurs, et (2) l'espace mémoire utilisé par les processeurs pour exécuter l'algorithme. La minimisation de l'espace mémoire est motivée pas de nombreux aspects : existence de réseaux (tels que les réseaux de capteurs) offrant des espaces mémoires limités, la minimisation des échanges de données entre processeurs voisins, la limitation du stockage d'information afin de pouvoir utiliser des techniques de redondance, etc. Ce séminaire présentera l'auto-stabilisation au travers deux grands problèmes classiques : la construction d'arbres couvrants, notamment d'arbres couvrants de poids minimum, et l'election d'un leader. Il présentera en particulier les liens entre auto-stabilisation et les techniques de décision distribuée, incluant le calcul de bornes inférieures sur l'espace mémoire nécessaire à la résolution par des algorithmes auto-stabilisants des problèmes susmentionnés.
MERCRED 03/07/2019 The Robust Capacitated Facility Location Problem, par Marco Caserta
Marco Caserta, IU Business School  
Salle B107, bâtiment B, Université de Villetaneuse
03/07/2019    14:00 - 15:00
Résumé :
We present robust formulations for the capacitated facility location problems under demand uncertainty, both for the single-source and the multi-source variants. Robustness is defined over different uncertainty sets, i.e., the box, ellipsoidal, and polyhedral uncertainty sets. For each of these variants, we define the robust counterpart and we compare the results obtained through an extensive computational study. We test the effect of using different support sets and analyze the performance of each robust variant using scenario curves and price of robustness, among other measures.
AOC 02/07/2019 Aspects combinatoires du problème de l'UCP, par Pierre Fouilhoux
Pierre Fouilhoux, Lip6 - Paris 6 - Sorbonne Université  
Salle B107, bâtiment B, Université de Villetaneuse
02/07/2019    12:30 - 13:30
Résumé :
Le problème classique appelé Unit Commitment Problem (UCP) est le problème central de planification de production d'électricité. Le problème combinatoire au coeur du problème de l'UCP est appéle le Min-up/min-down UCP (MUCP). Il consiste à déterminer un plan de production sur un horizon de temps discrétisé, pour un ensemble de centrales électriques. A chaque pas de temps, la production totale doit répondre à une demande connue. Chaque unité doit satisfaire des contraintes de temps minimum de fonctionnement et d'arrêt. Elle correspond également à des coûts de production et de mise en marche. Nous étudions comment la complexité du MUCP évolue en fonction du nombre d'unités et de période. Nous montrons en particulier que ce probl&egrav e;me est NP-difficile au sens fort. Nous présentons plusieurs aspects polyédraux d'une formulation PLNE pour le MUCP en nous intéressant à la combinatoire liant la production des unités entre les pas de temps. Pour cette formulation, l'espace des solutions exploré par un algorithme de branchement contient de nombreuses solutions symétriques et sous-symétriques: deux solutions symétriques (resp. sous-symétriques) pouvant être obtenues l'une de l'autre par permutation de ses composantes (resp. d'une partie de ses composantes). Nous proposons deux techniques bien distinctes pour briser ces symétries et accélérer la résolution. La première technique s'appuie sur l'étude du polyèdre des permutations et sur un algorithme, dit de fixing, utilisé à chaque noeud de l'algorithme de branchement. La deuxième technique repose sur des inégalités linéaires et des variables additionnelles. Enfin, nous présentons plusieurs aspects prometteurs sur une nouvelle décomposition de Dantzig-Wolfe qui utilise plusieurs inégalités issues de notre étude polyèdrale. Travaux réalisés avec Pascale Bendotti et Cécile Rottner.
MERCRED 26/06/2019 La Maison des Maths d'Ispahan, par Amir Hashemi
Amir Hashemi, Université Technologique d'Ispahan  
Salle B107, bâtiment B, Université de Villetaneuse
26/06/2019    14:00 - 15:00
Résumé :
Dans une première partie, je présenterai le système de recherche et enseignement supérieur des universités iraniennes et discuterai de ses performances. Dans une seconde partie, je présenterai les missions et activités des Maison des Mathématiques iraniennes, dont la première a été établie en 1999 à Ispahan. Il s'agit donc d'un exposé non technique, plutôt meta-scientifique. Il sera accompagné de quelques gâteaux iraniens.
AOC 25/06/2019 Optimisation et Bicliques, par Denis Cornaz
Denis Cornaz, LAMSADE - Paris Dauphine  
Salle B107, bâtiment B, Université de Villetaneuse
25/06/2019    12:30 - 13:30
Résumé :
Un sous-graphe partiel, d'un graphe donné, est une biclique, de ce graphe, s'il est biparti complet. D'abord, nous passerons en revue des résultats classiques admettant des preuves élégantes, voir surprenantes, autour de cette notion. Ensuite, nous mènerons une étude structurelle, particulière à cette notion, permettant de mettre en œuvre une technique générale d'optimisation (branch-and-cut, -and-price). Nous terminerons par une conjecture récemment démontrée.
RCLN 24/06/2019 Identity links in knowledge graphs, par Nathalie Pernelle
Nathalie Pernelle, LRI, Université Paris Sud  
Salle B107, bâtiment B, Université de Villetaneuse
24/06/2019    16:00 - 17:00
Résumé :
As the Web of Data continues to grow, more and more large datasets – covering a wide range of topics and domains – are being added to the Linked Open Data (LOD) Cloud. It is inevitable that different datasets, most of which are developed independently of one another, will come to describe (aspects of) the same thing, but will do so by referring to that thing by different names. Thanks to identity links, datasets that have been constructed independently of one another are still able to make use of each other’s information. Many data linking approaches have been defined that are rule-based. Some of these approaches exploit ontology axioms such as keys. However, these axioms are rarely specified in the available ontologies. In this seminar, I will present two approaches that aim to discover more or less expressive keys in RDF data. Then, since data linking approaches do not obtain a 100% precision, I will show that some approaches can focus on detecting incorrect sameAs links or detect that they are valid only in a specified semantic context.
A3 19/06/2019 Data Explainability Through Linguistic Expression of Extracted Knowledge, par Marie-Jeanne Lesot
Marie-Jeanne Lesot, LIP6  
Salle B107, bâtiment B, Université de Villetaneuse
19/06/2019    12:15 - 13:30
Résumé :
The pervasive use of data science techniques extracts regularities from available data for different tasks, such as prediction, characterisation or structuring. A current challenge is to improve the legibility of the obtained results, so as to allow a data expert to understand better the content of the data. One way to address this challenge consists in presenting them in natural language, offering linguistic expressions which may be easier to interpret for the user. The choice of such a result formulation then has an impact on the machine learning techniques to be applied to the data. The talk will illustrate these questions for numerical data as well as for time series, respectively discussing the extraction of gradual itemsets, that linguistically express knowledge about feature covariations, and the extraction of periodicity-related linguistic summaries, using the specific quantifier “regularly”. In both cases, as well as for enriched contextual variants, the question is to define precisely the associated semantics and to design efficient extraction algorithms. The talk will also discuss the issue of measuring the relevance of the linguistic terms used to express the summaries, both with respect to the data structure, in case of linguistic variables, and with respect to the cognitive interpretation, in case of approximate numerical expressions.
LOVE 18/06/2019 Parametric schedulability analysis of a launcher flight control system under reactivity constraints, par Jawher Jerray
Jawher Jerray, Équipe LoVe, LIPN  
Salle A303
18/06/2019    13:00 - 13:30
Résumé :
The next generation of space systems will have to achieve more and more complex missions. In order to master the development cost and duration of such systems, an alternative to a manual design is to automatically synthesize the main parameters of the system. We present an approach on the specific case of the scheduling of the flight control of a space launcher. The approach requires two successive steps: (1) the formalization of the problem to be solved in a parametric formal model and (2) the synthesis of the model parameters with a tool. We describe the problematic of the scheduling of a launcher flight control, then we show how this problematic can be formalized with parametric stopwatch automata; we then present the results computed by IMITATOR.
LOVE 18/06/2019 Towards parallel verification of concurrent systems using the Symbolic Observation Graph, par Hiba OUNI
Hiba OUNI, Équipe LoVe, LIPN  
A303
18/06/2019    12:30 - 13:00
Résumé :
An efficient way to cope with the combinatorial explosion problem induced by the model checking process is to compute the Symbolic Observation Graph (SOG). Given a stutter-invariant event-based LT L formula ?, involving a subset of actions (called observable actions), the SOG is a condensed representation of the state space graph based on a symbolic encoding of the nodes (sets of states linked with unobservable actions) and an explicit representation of the edges (labelled with observable actions). It has the advantage to be much reduced comparing to the original state space graph while being equivalent with respect to stutter-invariant temporal properties (i.e., the original system satisfies ? if and only if the corresponding SOG satisfies ?). Aiming to go fu rther in the process of tackling the state space explosion problem, we propose in this paper to parallelize the construction of the SOG using a hybrid approach (distributed+shared memory). Doing so, we take advantage of the recent advances in computer hardware, by distributing the construction process over a large number of multi-core processors. We studied the performances of our new approach comparing to both distributed and shared memory approaches on one side, and to the sequential construction on the other side. The obtained results show that the proposed approach offers an interesting alternative allowing to completely exploit the available distributed architecture while offering significant speedup.
LOVE 13/06/2019 La logique du signe : Sémiologie structuraliste et typage par biorthogonalité pour l'analyse de corpus., par Juan Luis Gastaldi
Juan Luis Gastaldi, ETH Zürich, SPHERE Paris Diderot  
Salle B107, bâtiment B, Université de Villetaneuse
13/06/2019    10:30 - 12:30
Résumé :
Dans cette conférence, il s'agira de présenter le cadre théorique et conceptuel d'une recherche en cours associant le projet d'une théorie formelle du signe d'inspiration structuraliste à certains principes et ressources de la linguistique de corpus et de la logique linéaire. L'objectif de ce travail interdisciplinaire est d'inférer de façon non supervisée des structures grammaticales ou logiques émergentes pour tout système de signes donné sous la forme d'un corpus d'expressions. L'analyse formelle proposée se base sur une procédure de segmentation stratifiée et de typage par biorthogonalité, capable, en principe, de capturer des structures de tous les niveaux (phonologiques ou graphématiques, morphologiques, syntaxiques et sémantiques). D'un point de vue philosophique, la perspective adoptée implique une manière originale de rapporter la logique au langage et à d'autres systèmes naturels de signes.
MERCRED 05/06/2019 Alice au pays des frises et des pavages, par François Bergeron
François Bergeron, UQAM  
Salle B107, bâtiment B, Université de Villetaneuse
05/06/2019    14:00 - 15:00
Résumé :
La notion de frise d’entiers a été introduite dans les années 1970 par Conway et Coxeter. Une telle frise correspond à un nombre fini de bandes horizontales superposées d’entiers positifs (>0), bornées au-dessus et en dessous par des bandes de 1, avec une condition locale liant ces entiers. Plus explicitement on demande que ad-bc=1, pour toute configuration locale de a, b, c, et d en forme de «?diamant?» (a et d se suivent sur une même ligne, avec b et c respectivement juste au-dessus et en dessous). Conway et Coxeter ont souligné que cela force un phénomène de répétition cyclique horizontale; de là le terme de frise. Un autre aspect fascinant est qu’ il n’y a qu’un nombre fini de telles frises ayant un nombre fixé de lignes, et qu’elles sont énumérées par les nombres de Catalan. Après un survol de cette notion et de sujets reliés, nous allons en considérer diverses généralisations. En particulier, on établira des liens avec la formule de condensation de Dogdson (l’auteur d’Alice au pays des merveilles) pour un calcul récursif de déterminants.
LOVE 23/05/2019 Towards a Combinatorial Proof Theory, par Ben Ralph
Ben Ralph, Inria Saclay  
Salle B107, bâtiment B, Université de Villetaneuse
23/05/2019    14:00 - 16:00
Résumé :
Combinatorial proofs have been introduced by Hughes to give a ``syntax-free'' presentations for proofs in classical propositional logic. In a nutshell, a classical combinatorial proof consists of two parts: (i) a linear part, and (ii) a skew fibration. The linear part encodes a proof in multiplicative linear logic (MLL), whose conclusion is given represented in a cograph, while the skew fibration maps this linear cograph to the cograph of the conclusion of the whole proof. For deep inference proofs, this skew fibration corresponds exactly to a contraction-weakening derivation. Applying certain restrictions to these two rules leads to substructural logics and substructural proof theory. These proof theoretic restrictions correspond precisely to set-theoretic and graph-theoretic restrictions on the skew fibration, allowing us to characterise proof systems by their graph homomorphism class.
A3 23/05/2019 Universal and best approximation through Bayesian ARTMAP, par Lucian SASU
Lucian SASU, Transilvania University of Brasov (Romenia)  
Amphi Ampere
23/05/2019    14:00 - 15:30
Résumé :
Bayesian ARTMAP is an adaptive resonance-theory based model, which was extended to perform regression. The network is shown to have both universal and best approximation properties. The network architecture and learning algorithm are presented, along with sketches of proofs and open questions.
LOVE 23/05/2019 Rigid species and normal functors over groupoids , par Zeinab Galal
Zeinab Galal, IRIF  
Salle B107, bâtiment B, Université de Villetaneuse
23/05/2019    10:30 - 12:00
Résumé :
Species of structures were introduced by Joyal as a unified framework for the theory of generating series in enumerative combinatorics. Species are connected to Girard's normal functor semantics of ?-calculus where terms are interpreted as power series with sets as coefficients. Fiore et al. presented a generalised definition that both encompasses Joyal's species and constitutes a model of differential linear logic (DiLL). For generalised species of structures, types are interpreted as groupoids which provides the connection with combinatorics whereas they are interpeted as sets in Girard's normal functors. To investigate how these models interact, we show that all the interpretations of proofs in DiLL actually live in a smaller fragment of generalised species called rigid species. These species correspond to the concept of free groupoid actions which provides us with a notion of normal functors over groupoids and allows us to bridge the gap between species and normal functors.
MERCRED 22/05/2019 Theoretical and Applied Research in Machine Learning, par Lucian SASU
Lucian SASU, Transilvania University of Brasov, Roumanie  
Salle B107, bâtiment B, Université de Villetaneuse
22/05/2019    14:00 - 14:45
Résumé :
Some insights and experiences in theoretical and applied research are shared. The two worlds are quite different and complementary. The presentation exposes challenging topics in industry which can be addressed through ML, along with hints for researchers willing to join industrial R&D departments.
RCLN 17/04/2019 Résumé de texte translingue par compression, par José Manuel Torres-Moreno
José Manuel Torres-Moreno, LIA, U.Avignon  
Salle B107, bâtiment B, Université de Villetaneuse
17/04/2019    14:30 - 15:30
Résumé :
Le Résumé Translingue de Textes (RTT) vise à générer un résumé dans une langue autre que le document source. Plus précisément, le RTT consiste à analyser un document dans une langue source pour en extraire sa signification, puis à générer un résumé court, informatif et correct dans une langue cible. Ce processus peut être divisé en deux processus principaux : le résumé et la traduction. Processus souvent antagonistes. Nous avons développé un cadré expérimentale pour générer des résumés translingues de documents en anglais, français, portugais, espagnol vers {anglais, français}. Nous avons utilisé des applications du TALN (résumé par extraction, similarité de phrases, compression de phrases et fusion multi-phrases) et des approches neuronales pour construire nos modèles de RTT. Cette présentation sera ciblée sur les techniques et les résultats obtenus lors de nos expériences.
LOVE 16/04/2019 Run-time Monitoring Approach for Hardware Trojans Dectection, par Maha Naceur
Maha Naceur, Université Paris 13  
Salle A303, bâtiment A, Université de Villetaneuse
16/04/2019    12:30 - 13:30
Résumé :
Today’s integrated circuits are vulnerable to malicious activities and alterations such as Hardware Trojan Horses (HTH), which can alter the functioning of the circuit, either during design or fabrication. Run-time monitoring is a predominantly used technique to validate a design in industry. Formal veri?cation overcomes the weakness of exhaustive simulation by applying mathematical methodologies to prove design correctness in an automated way. The design is analysed only against their functional characteristics, and their parametric behavior are do not considered in order to analyze the effects of HTHs. In this work, we present a new approach which focuses upon a combined technique that integrates the best characteristics of both run-time monitoring and formal veri?cation methods to provide an effective design validation tool which uses assertions to automatically generate synthesizable monitors capable for detecting hardware trojan horses at runtime
RCLN 04/04/2019 Apprentissage automatique à partir de données complexes et dynamiques: Application aux données textuelles, par Parisa RASTIN
Parisa RASTIN, LIPN  
Salle B107, bâtiment B, Université de Villetaneuse
04/04/2019    13:30 - 14:30
Résumé :
Les données actuelles sont de plus en plus variées et complexes et il est en général nécessaire d’adapter les algorithmes d’analyse à chaque type de description des données. Les algorithmes d’apprentissage devraient cependant pouvoir être fonctionnels quel que soit le type des données et la métrique choisie. Nous présentons dans cet exposé un algorithme de clustering relationnel basée sur le système de Coordonnées Barycentriques pour homogénéiser la représentation des objets et des prototypes et traiter de grands ensembles de données complexes. Dans le système de Coordonnées Barycentriques, l’espace de représentation est défini par un ensemble unique de points de support choisis parmi les objets de la base d'apprentissage. La définition d’un prototype correspond au calcul d’un objet dans l’espace barycentrique. À partir de ces approches, nous proposons un algorithme d'apprentissage basé sur un réseau de neurones artificiel défini dans l'espace barycentrique, adapté aux flux de données textuelles et permettant un suivit dynamique de l'évolution des données au cours du temps. Nous présenterons une applications concrètes sur l’extraction de domaines d’intérêt extraits d’URLS à partir de trace de navigation en ligne.
LOVE 02/04/2019 Continuous models of computation: computability, complexity,, par Amaury Pouly
Amaury Pouly, IRIF  
Amphy Ampère
02/04/2019    14:00 - 15:30
Résumé :
Et un cours abstract si nécessaire: In 1941, Claude Shannon introduced a continuous-time analog model of computation, namely the General Purpose Analog Computer (GPAC), [which can be implemented in practice through the use of analog electronics or mechanical devices]. In this talk, we review some recents results on the link between the GPAC and Turing machines. We will also see a surprising result on universal polynomial differential equations. Finally, I will also mention some recent application of this work to show that chemical reaction networks are strongly Turing complete with the differential semantics.
LOVE 02/04/2019 Fault-tolerant matrix factorisation: a formal model and proof, par Daniel Torres
Daniel Torres, LIPN, Équipe LoVe  
Salle A303, bâtiment A, Université de Villetaneuse
02/04/2019    12:30 - 13:30
Résumé :
As the size of high performance systems grows, tolerating failures has become a major issue in parallel computing. In this paper, we present a Coloured Petri Net model for a fault tolerant matrix factorisation algorithm. On the model, we prove resiliency properties and completion of the algorithm in presence of failures whatever the size of the input. This illustrates how formal modelling and verification techniques can help designing proofs on distributed algorithms.
27/03/2019 Journée IA du LIPN
 
Amphi Euler
27/03/2019    09:00 - 18:00
Résumé :
Cette journée est organisée par le Laboratoire d’Informatique de Paris Nord LIPN a pour but de présenter des travaux en intelligence artificielle, soit réalisés par des chercheurs du LIPN soit réalisés par des chercheurs extérieurs aussi bien académiques qu’industriels. Cette journée aura lieu dans l’amphithéâtre Euler de l’institut Galilée. L’inscription est gratuite mais obligatoire.
LOVE 19/03/2019 The size-change principle for mixed induction and coinduction, par Pierre Hyvernat
Pierre Hyvernat, Lama (Université de Savoie, Chambéry)  
C 304
19/03/2019    14:00 - 16:00
Résumé :
The Size-Change Principle (SCP) is a simple algorithm giving a partial termination test for recursive definitions. If the language is lazy, it also gives (by duality) a partial productivity test for recursive functions involving coinductive types. This is what is used in Agda. Unfortunately, when inductive and coinductive types are nested, this is unsound: there are "well typed" and terminating recursive definitions producing terms in empty types. Such definitions make Agda inconsistant. Using ideas from L. Santocanale about circular proof and parity games, I'll show how the SCP can be used to check "totality" of recursive definitions. Besides the SCP, the main ingredient is a more informative of call-graph, and I'll sketch the proof of correctness by defining their semantics using power domains.
LOVE 19/03/2019 Modeling, Analysis and Design of Critical Systems, par Prof. Nejib Ben Hadj-Alouane
Prof. Nejib Ben Hadj-Alouane, National Engineering School of Tunis (ENIT) - OASIS Lab (Optimization, Analysis of Industrial Systems and Services)  
Salle A303, bâtiment A, Université de Villetaneuse
19/03/2019    12:30 - 13:30
Document attaché
Résumé :
Our work on critical systems targets a number of problem areas and applications, all requiring the development of models for analysis and verification, and tools for decision making. This talk focuses on four different problem areas, each requiring a different modeling framework and solution approach. We begin by exposing our new Petri nets modeling framework, Extended Timed Petri Nets (ETPN), useful in modeling a special class of hybrid systems, with a weak continuous component and a strong discrete one, encountered when dealing with modern man-made, embedded and real-time systems. We discuss a supervisory control problem based on this framework, along with other related issues dealing with model transformation and complexity. Our second problem addresses operating high-demand and high-performance virtualized data centers (DCs). We focus on the development of tools, based on operations research models and techniques, for the management of theses DCs, while striving to improve user applications performance and productivity. We focus on the problem of virtual machines (VMs) placement in geographically distributed data centers. We consider communicating VMs assigned to data centers that are connected via a backbone network. We aim to plan and optimize the placement of VMs in data centers so as to minimize the IP-traffic within the backbone network along with user service interruption. Our third problem deals with security and in computer systems, services and protocols. We use the property of opacity to capture secrecy-related problems. We focus on the development of an on-line method for the efficient verification of opacity in models based on automata. We also extend opacity with the introduction of a quantification measure. Our fourth problem deals with sensor networks and their use in precision agriculture. We show that the development of application-oriented infrastructure management techniques, such a routing protocols, is important for modern Fog/IoT networks. Throughout our talk we discuss several research perspectives and applications linked to modern technologies, such as IoT, Web Services and Cloud/Fog computing.
LOVE 19/03/2019 Inequalities between plethysm coefficients and Kronecker coefficients via geometric complexity theory, par Christian Ikenmeyer
Christian Ikenmeyer  
Salle B107, bâtiment B, Université de Villetaneuse
19/03/2019    10:30 - 12:00
Résumé :
Research on Kronecker coefficients and plethysms gained significant momentum when the topics were connected to geometric complexity theory, an approach towards computational complexity lower bounds via algebraic geometry and representation theory. Both types of coefficients appear independently in R. Stanley's list of "Positivity problems and conjectures in algebraic combinatorics". This talk is about a result that was obtained with geometric complexity theory as motivation, namely an inequality between rectangular Kronecker coefficients and plethysm coefficients. The proof interestingly uses insights from algebraic complexity theory. As far as we are aware, algebraic complexity theory has never been used before to prove an inequality between representation theoretic multiplicities. This is joint work with Greta Panova (Rectangular Kronecker coefficients and plethysms in geometric complexity theory, Adv Math 2017).
RCLN 11/03/2019 Structure Prediction Energy Network (SPEN) using Dual Decomposition on Dependency Parsing, par Xudong ZHANG
Xudong ZHANG, LIPN - RCLN  
Salle B107, bâtiment B, Université de Villetaneuse
11/03/2019    14:00 - 15:00
Résumé :
Dependency Parsing is one of the basic tasks in the field of Natural Language Processing (NLP). The goal is to find whether there exist a strong relationship between different words in a sentence. It can be used as the basic step of many NLP systems like question answering system. Solving a dependency parsing problem can be realized by a energy based network with the output of the neural network as a scalar (energy). The goal is to find the most compatible structure (a graph) with the input sentence and the most compatible structure is supposed to give the lowest energy for the neural network. As the structure of the sentence should be a tree (one root, every word has and only has one pa rent, no circle), to simplify the problem, people always construct a linear function corresponding to the structure that we want to find, i.e. we suppose different arcs are independent. However, this method may limit the capacity of the system to describe more complex relations. In this project, inspired by the idea of Structure Prediction Energy Network (SPEN), we construct a new neural network which is composed of two parts, i.e. local energy part and global energy part. We showed that it is possible to solve the problem with dual decomposition when we have a convex (non-linear) function for the global energy part together with the linear local energy part. As one part of my Phd thesis, this work is still ongoing.
A3 28/02/2019 Apprentissage statistique dans un contexte décentralisé et applications à la vision par ordinateur, par David Picard
David Picard, ENSEA Cergy-Pontoise  
Salle B107, bâtiment B, Université de Villetaneuse
28/02/2019    12:15 - 13:45
Résumé :
L'apprentissage statistique est de nos jours incontournable dans un certain nombre de tâches complexes, notamment dans le traitement des données multimédia comme la vision. Pour gagner en précision, des modèles de plus en plus complexes sont entraînés sur des volumes de données de plus en plus gros. Cependant, la répartition naturelle des données auprès des capteurs qui les ont crées laisse à penser qu'il serait préférable d'apprendre ces modèles sans collecter les données d'apprentissage auprès d'un calculateur central. Nous présentons dans cet exposé un paradigme d'apprentissage décentralisé asynchrone pour répondre à ce problème. Nous considérons le cas ou plusieurs calculateurs optimisent un modèle statistique à l'aide de données locales et coopèrent afin d'obtenir un modèle consensus. Nous montrons comment transposer des algorithmes d'apprentissage connus (k-means, PCA, SVM, deep learning) à ce paradigme, ainsi que des preuves de leur équivalence avec les versions centralisées. Enfin, nous montrons plusieurs exemples d'applications de ces modèles à des tâches de vision par ordinateur.
LOVE 27/02/2019 Monoides et algèbres de tris sur les groupes de coxeter, par Nicolas Thiéry
Nicolas Thiéry  
B311
27/02/2019    15:22 -
Résumé :

Le séminaire LCR accueille Nicolas Thiéry (Université Paris 11).

Le modèle combinatoire usuel pour décrire la 0-algèbre de Hecke H_n(0) (en type A) est de considérer l'algèbre (ou le monoïde) engendré par les opérateurs de tri-à-bulle élémentaires pi_i, i=1...n-1 définis comme suit: pi_i agit sur un mot de longueur n en triant les lettres en position i et i+1. Cette construction se généralise naturellement pour tout groupe de Coxeter fini.

En combinant ces opérateurs avec plusieurs variantes (tri croissant / décroissant / affine), nous construisons un certain nombre de monoïdes et algèbres. De manière étonnante en premier abord, ceux-ci se retrouvent munis d'une structure très riche, faisant intervenir la combinatoire des descentes (et une généralisation de celle-ci), les ordres usuels sur les groupes de Coxeter (Bruhat, permutohèdre gauche et droit), ainsi que de nouveaux ordres. Cette structure s'explique par de nombreuses connections avec la théorie des représentations, l'algèbre de Hecke affine, les fonctions symétriques, etc.

LOVE 27/02/2019 Une formalisation des actes de language en ludique (et quelques remarques générales sur l'utilisation de la logique en shs), par s et Samuel Tronçon
s et Samuel Tronçon  
B 311, LIPN
27/02/2019    15:22 -
Résumé :

Les séminaires LCR et RCLN accueillent Samuel Tronçon (Centre d'Epistémologie et d'Ergologie Comparative et Institut de Mathématiques de Luminy).

Nous proposons une formalisation des actes de langage dans le cadre formel de la Ludique. Nous définissons un acte de langage ludique (ALL) comme une structure exécutable apte à remplir certains tests, et dont l'interaction produit une modification du contexte. Notre modèle possède deux couches de représentation. La première, la plus primitive, est constituée par les interactions en contexte. Elle comprend donc les structures qui supportent l'acte de langage. La seconde, plus abstraite, est le résultat de catégorisations réalisées par les agents, sur la base des interactions réelles entre actes de langage et avec le contexte. Cette double articulation ouvre la voie à la prise en compte du caractère relatif des actes en fonction de sa structure, du contexte et de l'observateur.

LOVE 27/02/2019 (annulé pour cause de grève) une formalisation des actes de langage en ludique" (et quelques remarques générales sur l'utilisation de la logique en shs), par s et Samuel Tronçon
s et Samuel Tronçon  
B311
27/02/2019    15:22 -
Résumé :

(ANNULE pour cause de GREVE)

Les séminaires LCR et RCLN accueillent Samuel Tronçon (Institut de Mathématiques de Luminy et Paris 8).

Nous proposons une formalisation des actes de langage dans le cadre formel de la Ludique. Nous définissons un acte de langage ludique (ALL) comme une structure exécutable apte à remplir certains tests, et dont l'interaction produit une modification du contexte. Notre modèle possède deux couches de représentation. La première, la plus primitive, est constituée par les interactions en contexte. Elle comprend donc les structures qui supportent l'acte de langage. La seconde, plus abstraite, est le résultat de catégorisations réalisées par les agents, sur la base des interactions réelles entre actes de langage et avec le contexte. Cette double articulation ouvre la voie à la prise en compte du caractère relatif des actes en fonction de sa structure, du contexte et de l'observateur.

LOVE 27/02/2019 La plateforme why de vérification déductive de programmes c et java, par J.C. Filliâtre.
J.C. Filliâtre.  
B311
27/02/2019    15:22 -
Résumé :

Le séminaire LCR accueille Jean-Christophe Filliâtre (CNRS Université Paris 11).

Cet exposé présente la plateforme Why (http://why.lri.fr/), un ensemble de techniques et d'outils développés dans le projet ProVal pour la vérification de propriétés fonctionnelles de codes C et Java. La plateforme Why s'appuie sur plusieurs principes :
(1) la spécification des programmes par l'intermédiaire d'annotations dans le source, en utilisant des langages inspirés de JML ;
(2) un calcul de plus faibles préconditions reposant sur un modèle mémoire de type Burstall-Bornat raffiné par une analyse statique de séparation ; et enfin
(3) la possibilité d'utiliser un grand nombre d'outils de preuve existants, tant automatiques qu'interactifs, pour décharger les obligations de preuve.

LOVE 27/02/2019 (annulé pour cause de grève) monoides et algèbres de tris sur les groupes de coxeter, par N. Thiéry
N. Thiéry  
B311
27/02/2019    15:22 -
Résumé :

(ANNULE pour cause de GREVE)

Le séminaire LCR accueille Nicolas Thiéry (Université Paris 11).
(Travail commun avec Florent Hivert et Anne Schilling)

Le modèle combinatoire usuel pour décrire la 0-algèbre de Hecke H_n(0) (en type A) est de considérer l'algèbre (ou le monoïde) engendré par les opérateurs de tri-à-bulle élémentaires pi_i, i=1...n-1 définis comme suit: pi_i agit sur un mot de longueur n en triant les lettres en position i et i+1. Cette construction se généralise naturellement pour tout groupe de Coxeter fini.

En combinant ces opérateurs avec plusieurs variantes (tri croissant/décroissant/affine), nous construisons un certain nombre de monoïdes et algèbres. De manière étonnante en premier abord, ceux-ci se retrouvent munis d'une structure très riche, faisant intervenir la combinatoire des descentes, ainsi que les ordres usuels sur les groupes de Coxeter (Bruhat, permutohèdre gauche et droit). Cette structure s'explique en fait par de nombreuses connections avec la théorie des représentations, l'algèbre de Hecke affine, les fonctions symétriques, etc.

LOVE 27/02/2019 Fractional calculus: definitions, numerical methods and applications in control systems and multi-Scale processes, par Z. Odibat
Z. Odibat  
B311
27/02/2019    15:22 -
Résumé :

Le séminaire LCR accueille Zaid Odibat (Al-Balqa' Applied University, Jordan).

Recently, the fractional derivative has drawn much attention due to its wide application in various fields of physics and engineering. Fractional derivatives provide an excellent instrument for the description of memory and hereditary properties of various materials and processes. The main reason for using the integer-order models was the absence of solution methods for fractional differential equations. The real objects of using fractional-order models are that we have more degrees of freedom in the model and that a memory is included in the model. Fractional-order systems have an unlimited memory.

In this presentation, we will, first, introduce the most used definitions of fractional derivatives and their properties then we will highlight some comments about differential equations of fractional order. Second, we will give an overview of the recent analytical-approximate methods that are used to provide approximate solutions for nonlinear differential equations of fractional order. Finally, we will introduce some important areas of applications, where the use of fractional order models is expected to be very suitable and useful. Theses areas included the control systems and the multi-scale processes.

LOVE 27/02/2019 An introduction to size-Change termination analysis, par A. Ben-Amram
A. Ben-Amram  
B311
27/02/2019    15:22 -
Résumé :

Le séminaire LCR accueille Amir Ben-Amram(The Academic College of Tel-Aviv).

This talk describes an approach to the problem of determining whether a program terminates for all input data.

The basic idea of Size-Change Termination (SCT) is to prove that in any (hypothetic) infinite computation by the program, an infinite descent in some data arises. When the data considered are drawn from a well-founded set (typically the natural numbers), infinite descent is impossible, and the logical conclusion is: no actual computation path can be infinite.

The approach subsumes the usual methods of proving termination by observing that "something decreases" in each loop, e.g., lexicographic descent of a tuple of variables.

But how can the desired property be proven? The SCT technique relies on Size Change Graphs, a convenient abstraction of program behaviour. Using these graphs, it is possible to formulate the condition of interest in combinatorial terms, which helped to get several results, the first of which was that the property is decidable.

Subsequent work identified the complexity class of the problem (complete for PSPACE), investigated different algorithms (including efficient approximations), showed how to abstract different kinds of programs (functional, imperative, high-order, TRS...), and a lot more. This talk will be mostly introductory and include a brief exposition of results from the research of the speaker and his colleagues.

LOVE 27/02/2019 Réécriture, catégories d'ordre supérieur, et expressivité des modèles de calcul concurrent, par D. Mazza
D. Mazza  
B311
27/02/2019    15:22 -
Résumé :
Le séminaire LCR accueille Damiano Mazza (LIPN).

Un problème fondamental dans la comparaison de différents modèles du parallélisme et de la concurrence est celui de définir la notion de codage, ou de traduction. A ce jour, parmi toutes les notions universellement acceptées de codage entre modèles concurrents, il n'en existe aucune qui s'impose nettement sur les autres. Nous proposons d'étudier la notion de codage en partant de la vision du calcul comme réécriture, et en utilisant des notions venant de la théorie des catégories d'ordre supérieur et de la théorie des structures d'évenements de Winskel.

LOVE 27/02/2019 Descriptions algébriques et logiques de graphes finis, par B. Courcelle
B. Courcelle  
B311
27/02/2019    15:22 -
Résumé :

Le séminaire LCR accueille Bruno Courcelle (Labri).

De manière à étendre aux graphes les concepts fondamentaux de la Théorie des Langages Formels, on définit sur l'ensemble des graphes finis deux structures d'algèbre (de "magma" selon une terminologie obsolète) qui généralisent la structure de monoïde libre. On en déduit de manière immédiate des notions de reconnaissabilité (par congruences finies) et d'algébricité (par systèmes d'équations à points fixes) pour les graphes , et