Seminars

Links' Seminars and Public Events Add to google calendar
2017
Wed 1st Feb
11:00 am
12:30 pm
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Pierre Bourhis: The Chase
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Inria Lille
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

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