Links' Seminars and Public Events |
2016 | |
---|---|
Fri 19th Feb 11:00 am 3:00 pm | CNRS, Université Lens |
Thu 21st Jan 11:00 am 1:00 pm | 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 reachability. 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. "Lille-Salle B21" |
Thu 14th Jan all day | visite pierre senellart |
Tue 12th Jan to Thu 14th Jan all day | visite Antoine Amarilli |
2015 | |
Mon 14th Dec 2:00 pm 4:00 pm | Slawek Staworko's HDR defense: "Symbolic Inference Methods for Databases" M2, salle de réunion |
Fri 20th Nov 10:30 am 12:30 pm | 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. "Lille-Salle B21" |
Fri 13th Nov 10:30 am 12:00 pm | Seminar Links by Iovka Boneva: "Shape Expressions Schemas" Abstract: 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. "Lille-Salle B21" |