Conference Torrents
28 janvier 2013 - 10h-11h30
ONERA Toulouse - Salle du Boulon
Using non-convex approximations for efficient analysis of timed automata
Presented by Frédéric Herbreteau, Laboratoire Bordelais de Recherche en Informatique
(LABRI)
The reachability problem for timed automata asks if there exists a path from an initial state
to a target state. The standard solution to this problem involves computing the zone graph
of the automaton, which in principle could be infinite. In order to make the graph finite,
zones are approximated using an extrapolation operator. For reasons of efficiency in current
algorithms, extrapolation of a zone is always a zone; and in particular it is convex.
We propose to solve the reachability problem without such extrapolation operators. To
ensure termination, we provide an efficient algorithm to check if a zone is included in the
aLU abstraction of another. Although theoretically better, aLU cannot be used in the
standard algorithm since an abstraction of a zone may not be convex.
An additional benefit of the proposed approach is that it permits to calculate approximating
parameters on-the-fly during exploration of the zone graph, as opposed to the
current methods which do it by a static analysis of the automaton prior to the exploration.
This allows for further improvements in the algorithm. Promising experimental results are
presented.