|Links' Seminars and Public Events|
Mon 11th Jul
to Tue 12th Jul
Mon 27th Jun
Colis ANR project: general meeting
Inria Paris, Salle 119 "Ada Lovelace"
Fri 24th Jun
Fatima Belkouch: on the hypercube algorithm for conjunctive queries
Abstract: We consider the problem of computing a conjunctive query on a large database in a parallel setting with p servers. Unlike traditional query processing, the complexity is no longer dominated by the number of disk accesses. Typically, a query is evaluated by a sufficiently large number of servers such that the entire data can be kept in the main memory of these servers. The dominant cost becomes that of communicating data and synchronizing among the servers.
I will present some interesting results in [1, 2, 3, 4] dealing with the communication complexity of massively parallel computation of a query. The computation is performed in "rounds".
First, I will present the Massively Parallel Communication (MPC) model to analyze the tradeoff between the number of rounds and the amount of communication required in a massively parallel computing environment.
Then I will present the HyperCube (HC) algorithm that computes a full conjunctive query q in one round.
I will discuss the communication complexity . The main result is the optimal load O(m/p1/τ ) where τ is the fractional vertex cover of the hypergraph of q and m the input data size.
 Parallel Evaluation of Conjunctive Queries. Paris Koutris, Dan Suciu PODS2011
 Communication Steps for Parallel Query Processing. Paul Beame, Paris Koutris, Dan Suciu PODS2013
 Skew in Parallel Query Processing. Paul Beame, Paris Koutris Dan Suciu PODS'2014
 Worst-Case Optimal Algorithms for Parallel Query Processing. Paris Koutris, Paul Beame, Dan Suciu ICDT2016
Thu 23rd Jun
Victor Vianu in Polaris
Thu 23rd Jun
victor vianu visit
Mon 20th Jun
to Wed 22nd Jun
journee scientique inria à rennes
Fri 17th Jun
PhD Thesis Defense by Tom Sebastian: Evaluation of XPath Queries on XML streams with Networks of Early Nested Word Automata
The challenge that we tackle in this thesis is the problem of how to answer
XPath queries on XML streams with low latency, full coverage, high time
efficiency, and low memory costs. We first propose to approximate earli-
est query answering for navigational XPath queries by compilation to early
nested word automata. It turns out that this leads to almost optimal la-
tency and memory consumption. Second, we contribute a formal semantics
of XPath 3.0. It is obtained by mapping XPath to the new query language
λXP that we introduce. We then show how to compile λXP queries to net-
works of early nested word automata, and develop streaming algorithms for
the latter. Thereby we obtain a streaming algorithm that indeed covers all of
XPath 3.0. Third, we develop an algorithm for projecting XML streams with
respect to the query defined by an early nested word automaton. Thereby
we are able to make our streaming algorithms highly time efficient. We have
implemented all our algorithms with the objective to obtain an industrially
applicable streaming tool. It turns out that our algorithms outperform all
previous approaches in time efficiency, coverage, and latency.
Thu 16th Jun
Nicolas Bacquey Links seminar: Introduction to uniform periodical computation : leader election on periodical cellular automata
Thu 16th Jun
Hubie Chen, Semainar and Visit
Fri 22nd Apr
Assemblée générale Inria Lille
Fri 1st Apr
Laurent d'Orazio (cancelled)
Fri 25th Mar
Datacert ANR project: general meeting
Fri 18th Mar
Charles Paperman: "Streaming and circuit complexity"
In this talk, I will present a connection between the streaming complexity and the circuit complexity of regular languages through a notion of streaming by block . This result provides tight constructions of boolean circuits computing an automaton, thanks to some classical and recent results on the circuit complexity of regular languages. I will apply this framework to the schema validation in streaming of XML-documents.
Fri 18th Mar
Visit of Charles Paperman, Université Paris 7
Fri 11th Mar
Seminar Links by Sylvain Salvati: Behavioral verification of higher-order programs
Abstract: Higher-order constructions make their way into main stream
programming languages like Java, C++, python, rust... These
constructions bring new challenges to the verification of programs as
they make their control flow more complex.
In this talk, I will present how methods coming from denotational
semantics can prove decidable the verification of certain properties of
higher-order programs. These properties are expressed by means of finite
state automata of the possibly infinite execution trees generated by the
programs and can capture safety properties but also liveness and
Fri 11th Mar
Sylvain Salvati: visit and Talk
Université Bordeaux 1
Wed 9th Mar
cristan duriez 30 minutes de science inria lille
Fri 4th Mar
Colis ANR project: general meeting
Inria Lille, Salle B21
Thu 3rd Mar
Kim Nguyen: visit for discussion with Links' members (no talk)
Université Paris Sud
Fri 19th Feb
CNRS, Université Lens
Thu 21st Jan
Seminar by Vincent Penelle: "Rewriting high-order stack trees"
Higher-order pushdown systems and ground tree rewriting systems can
be seen as extensions of suffix word rewriting systems. Both classes
generate infinite graphs with interesting logical
properties. Indeed, the satisfaction of any formula written in
monadic second order logic (respectively first order logic with
reachability predicates) can be decided on such a graph.
The purpose of this talk is to propose a common extension to both
higher-order stack operations and ground tree rewriting. We introduce a model
of higher-order ground tree rewriting over trees labelled by
higher-order stacks (henceforth called stack trees), which syntactically
coincides with ordinary ground tree rewriting at order 1 and with the dynamics
of higher-order pushdown automata over unary trees. The infinite
graphs generated by this class have a decidable first order logic with
Formally, an order n stack tree is a tree labelled by order n-1 stacks.
Operations of ground stack tree rewriting are represented by a certain class
of connected DAGs labelled by a set of basic operations over stack trees
describing of the relative application positions of the basic
operations appearing on it. Applying a DAG to a stack tree t intuitively
amounts to paste its input vertices to some leaves of t and to simplify
the obtained structure, applying the basic operations labelling the edges of the
DAG to the leaves they are appended to, until either a new stack tree is
obtained or the process fails, in which case the application of the DAG to t
at the chosen position is deemed impossible. This model is a common extension
to those of higher-order stack operations presented by Carayol and of ground tree
transducers presented by Dauchet and Tison.
As further results we can define a notion of recognisable sets of
operations through a generalisation. The proof that the graphs generated
by a ground stack tree rewriting system have a decidable first order theory
with reachability is inspired by the technique of finite set interpretations
presented by Colcombet and Loding.
Thu 14th Jan
visite pierre senellart
Tue 12th Jan
to Thu 14th Jan
visite Antoine Amarilli
Mon 14th Dec
Slawek Staworko's HDR defense: "Symbolic Inference Methods for Databases"
M2, salle de réunion
Fri 20th Nov
Seminar Links by Stéphane Demri: "Separation Logic and Friends"
Abstract: Separation logic is used as an assertion language for
Hoare-style proof systems about programs with pointers,
and there is an ongoing quest for understanding its
complexity and expressive power. There are also
a lot of activities to develop verification methods
with decision procedures for fragments of practical use.
Actually, there exist many variants for separation
logic that can be viewed as fragments of second-order logic,
as well as variants of modal or temporal logics in which
models can be updated dynamically.
In this talk, after introducing first principles on separation logic,
issues related to decidability, computational complexity and expressive
power are discussed. We provide several tight relationships with
second-order logics, interval temporal logics or data logics, depending
on the variants of the logic and on the syntactic resources available.
Fri 13th Nov
Seminar Links by Iovka Boneva: "Shape Expressions Schemas"
Shape Expressions Schemas is an expressive schema and constraint language for RDF data. I am going to define the language, illustrate it with examples, then give a validation algorithm and talk about ongoing work.
Thu 29th Oct
Seminar Links by Antoine Amarilli
Fri 9th Oct
Seminar Links: Adrien Boiret
Thu 1st Oct
Seminar Links by Eric Prud'hommeaux: Shape Expressions: (finally) a schema language for RDF graph structure
Initial architects envinsioned RDF as a knowledge representation language, freeing users from syntactic limitations and revolutionizing the way information was exchanged.
While inference and description logic are applied to RDF, the foundation of simple assertions composed of global, unambiguous identifiers, has many more mondane and practical applications.
Distributed contributions to large (web-scale) data graphs demands adaptation of tree and stream-based validation techniques to operate over a graph.
Shape Expressions performs an ordered traversal of RDF graphs to
1 validate of structural constraints.
2 perform generative semantic actions.
Fri 11th Sep