Links' Seminars and Public Events |

2018 | |
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Fri 27th Apr 10:30 am 12:30 pm | Yann Strozecki in Links' Seminar: Methods in enumerationIn enumeration we are interested in generating a set of solutions, while bounding the time needed to generate one solution. We will first present the complexity measures used in this context, simple theoritical results and a few open questions. We then introduce classical problems in this area such as the enumeration of: trees, models of a DNF, model of a FO or MSO formula, the maximal cliques of a graph, circuits of a matroid ... We use them to illustrate the algorithmic toolbox of enumeration (Gray Code, backtrack search, reverse search, saturation...). Lille B21 |

Wed 25th Apr 2:15 pm 3:45 pm | Nicolas StageJan's office |

Fri 20th Apr 2:15 pm 3:45 pm | Nicolas StageJan's office |

Fri 13th Apr 2:15 pm 3:45 pm | Nicolas StageJan's office |

Fri 13th Apr 10:00 am 12:00 pm | Iovka Boneva and Jérémie Dusart in Links' Seminar: Shape Expressions Schemas 2.0 : Semantics and ImplementationWe will present the semantics of the ShEx language, its implementation in java, and future directions of research. Salle B21 |

Fri 6th Apr 2:15 pm 3:45 pm | Nicolas StageJan's office |

Fri 30th Mar 2:15 pm 3:45 pm | Nicolas StageJan's office |

Fri 23rd Mar 10:00 am 11:30 am | Paul Gallot: High-Order Tree TransducersPaul présentera le papier de Sylvain, Aurélien et Paul, soumis à LICS 2018, sur le sujet des transducteurs d'arbres d'ordre supérieur. |

Wed 21st Mar 2:00 pm 3:15 pm | répétition Delta |

Fri 16th Mar 10:00 am 11:30 am | Luc Dartois in Links' Seminar: A Logic for Word Transductions with SynthesisIn this talk I present a logic, called LT, to express properties of transductions, i.e. binary relations from input to output (finite) words. I argue that LT is a suitable candidate as a specification language for verification of non reactive systems, extending the successful approach of verifying synchronous systems via Mealy Machines and MSO. In LT, the input/output dependencies are modelled via an origin function which associates to any position of the output word, the input position from which it originates. LT is well-suited to express relations (which are not necessarily functional), and can express all regular functional transductions, i.e. transductions definable for instance by deterministic two-way transducers. Despite its high expressive power, LT has decidable satisfiability problems. The main contribution is a synthesis result: it is always possible to synthesis a regular function which satisfies the specification. Finally, I explicit a correspondence between transductions and data words. As a side-result, we obtain a new decidable logic for data words. Inria Lille |

Fri 9th Mar 10:00 am 11:00 am | Benjamin Bergougnoux : Counting minimal transversals of hypergraphsA transversal of a hypergraph H is a subset of vertices that intersects all the hyper-edges H. The enumeration and the counting of the minimal transversals have a lot of applications in many domains (graph theory, AI, datamining, etc). Counting problems are generally harder than theirs associated decision problems. For example, finding a minimal transversal is doable in polynomial time but counting them is #P-complet (the equivalent of NP-complet for counting problems). We have proved that we can count the minimal transversals of any beta-acyclique hypergraph in polynomial time. Our result is based on a recursive decomposition of the beta-acyclique hypergraph founded by Florent Capelli and by the introduction of a new notion that generalize the minimal transversals. A lot of exciting open questions live in the neighborhood of our result. In particular, our algorithm is able to count the minimum dominating set of a strong-chordal graph. But counting the minimum dominating set is #P-complete on split graphs. Is it the beginning of a complete characterization of the complexity of counting minimal dominating sets in dense graphs ? Salle B21 |