Decidability and Complexity Issues for One-Counter Machines

Antonin Kucera
Masaryk University Brno
(Visiting Faron Moller for one week.)

One-counter machines can be seen as an idealized model for finite-state programs operating on a single unbounded variable. We present an overview of recent results related to the problem of formal verification of reactive systems defined in the syntax of one-counter machines. More specifically, we consider the problem of equivalence-checking (wrt bisimilarity and simulation equivalence) and the model-checking problem for branching-time logics (EF, mu-calculus). It turns out that a very important feature of one-counter systems which often determines the decidability/tractability border for the mentioned problems is the ability to test the counter for zero. We also consider `weak' one-counter machines which cannot test for zero explicitly (this model is computationally equivalent to Petri nets with at most one unbounded place) and show that this weakening indeed brings more decidability and tractability.

The presentation is based on several papers which appeared in the last five years, including some very recent ones. The aim is to present the results themselves together with some notes on proof techniques, without going into technicalities.

ASTEC seminar
February 27, 2001

Place: Information technology, Uppsala University
Room: 1510
Time: 13.15-14.00 (+ discussions)

Room 1510 is in Building 1, Floor 5, room 10 (in the southern part of the building).

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There will be an extended period for discussions after the seminar.

Speakers are encouraged to give an short (5 min) introduction to the subject at the begining of the talk.
Listeners are excused if they have to leave after 14.00.

Everyone is welcome !

Updated 16-Feb-2001 09:20 by Roland Grönroos
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