Seminars

Links' Seminars and Public Events Add to google calendar
2017
Fri 20th Jan
10:30 am
12:30 pm
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Pierre Bourhis: "Tree Automata for Reasoning in Databases and Artificial Intelligence"
In database management, one of the principal task is to optimize the queries to evaluate them efficiently. It is in particular the case for recursive queries for which their evaluation can lead to crawl all the database. In particular, one of the main question is to minimize the queries in order to avoid to evaluate useless parts of the query. The core theoretical question around this line of work is the problem of inclusion of a query in another. Interestedly, this question is related to an important question in IA which is to answer a query when the data is incomplete but rules are given to derive new information. This problem is called certain query answering. In both context, if both problem are undecidable in general, there are fragments based on guardedness that are decidable due to the fact there exists witness of the problems that have a bounded tree width and that their encoding in trees is regular. Furthermore, the queries can be translated in MSO. In both contexts, Courcelle’s Theorems imply the decidability of both problems. I will present to the different results on the translation of logic class of formula for our problems into tree automata to obtain tight bounds to the problems of inclusion of recursive queries or certain query answering.

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Inria Lille
Wed 11th Jan
2:15 pm
3:25 pm
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Michael vanden Boom, Oxford University : Decidable fixpoint logics
Fixpoint logics can express dynamic, recursive properties, but often fail to have decidable satisfiability. A notable exception to this is the family of well-behaved "guarded" fixpoint logics,
which subsume a variety of query languages and integrity constraints of interest in databases and knowledge representation. In this talk, I will survey some recent results about these logics.
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Lille B21
Mon 9th Jan
to Fri 13th Jan
 all day
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Visite Michael vanden Boom, Oxford University
2016
Fri 9th Dec
 all day
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Kickoff Headwork
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Paris MNHN
Fri 18th Nov
10:30 am
12:00 pm
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Florent Capelli Links Seminar
"Lille-Salle B21"
Fri 18th Nov
 all day
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Florent Capelli visit
Tue 8th Nov
2:30 pm
4:30 pm
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Seminar Link by Helmut Seidl: "Equivalence of Deterministic Top-Down Tree-to-String Transducers is Decidable"
Abstract:

We show that equivalence of deterministic top-down tree-to-string transducers is decidable,
thus solving a long standing open problem in formal language theory.
We also present efficient algorithms for subclasses:
polynomial time for total transducers with unary output alphabet (over a given top-down regular domain language),
and co-randomized polynomial time for linear transducers, these results are obtained using techniques from multi-linear algebra.
For our main result, we prove that equivalence can be certified by means of inductive invariants using polynomial ideals.
This allows us to construct two semi-algorithms, one searching for a proof of equivalence, one for a witness of non-equivalence.
"Lille-Salle B31 "
Mon 7th Nov
2:00 pm
4:00 pm
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PhD defense Adrien Boiret
Fri 4th Nov
 all day
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colis general meeting
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Paris
Thu 27th Oct
10:00 am
6:00 pm
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Links day
Thu 27th Oct
 all day
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links day
Thu 20th Oct
2:00 pm
4:00 pm
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Seminar Links by Vincent Hugot: "Top-Down Transducers for Data Trees"
Abstract:
Tree transducers have a wide range of application domains ranging from compiler construction,
program analysis, and computational linguistics, to semi-structured databases and file system
transformations. A common application of these domains is to specify and verify transformations
of data trees, i.e., trees whose nodes are labeled by data values from an infinite domain. Most
existing classes of tree transducers and their formal studies, however, are restricted to trees over
finite signatures without data. In this paper, we lift the most prominent class of top-down tree
transducers to data trees, such that its good properties are preserved. In particular, we show that
top-down transducers for data trees have a decidable equivalence problem, without imposing any
linearity restriction as in previous approaches based on symbolic top-down tree transducers.
"Lille-Salle B21"
Thu 13th Oct
2:00 pm
5:30 pm
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comité de projet
Thu 13th Oct
2:00 pm
3:00 pm
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Seminar Christof Löding
"Lille-Salle B21"
Thu 13th Oct
to Fri 14th Oct
 all day
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visit christof löding

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