12 research outputs found
Benchmarks for Parity Games (extended version)
We propose a benchmark suite for parity games that includes all benchmarks
that have been used in the literature, and make it available online. We give an
overview of the parity games, including a description of how they have been
generated. We also describe structural properties of parity games, and using
these properties we show that our benchmarks are representative. With this work
we provide a starting point for further experimentation with parity games.Comment: The corresponding tool and benchmarks are available from
https://github.com/jkeiren/paritygame-generator. This is an extended version
of the paper that has been accepted for FSEN 201
Stuttering equivalence is too slow!
Groote and Wijs recently described an algorithm for deciding stuttering
equivalence and branching bisimulation equivalence, acclaimed to run in
time. Unfortunately, the algorithm does not always meet
the acclaimed running time. In this paper, we present two counterexamples where
the algorithms uses time. A third example shows that the
correction is not trivial. In order to analyse the problem we present
pseudocode of the algorithm, and indicate the time that can be spent on each
part of the algorithm in order to meet the desired bound. We also propose fixes
to the algorithm such that it indeed runs in time.Comment: 11 page
Modelling and verifying IEEE Std 11073-20601 session setup using mCRL2
In this paper we advocate that formal verification should bea part of the development of a communication standard;in a short period of time issues areuncovered that have been in the standard for a number of years, and allsubtleties in the correctness of the protocol are understood.We model and verify the session setup protocolthat is part of the IEEE 11073-20601:2008 standard for communication betweenpersonal health devices.We identify a number of issues present in the standards document.Discussion with a member of the standards committee unveiled that most, but notall, of the identified issues are fixed in the IEEE 11073-20601:2010 version ofthe standard.In addition, the correctness of the protocol, including the fixes, is assessed.For this, properties of the session setup protocol are formulated, and usingthe model checker mCRL2 it is verified whether the model satisfies theseproperties.We show that the session setup protocol is flawed, and propose a straightforwardway to fix this issue
Expressiveness Results for Timed Modal Mu-Calculi
This paper establishes relative expressiveness results for several modal
mu-calculi interpreted over timed automata. These mu-calculi combine modalities
for expressing passage of (real) time with a general framework for defining
formulas recursively; several variants have been proposed in the literature. We
show that one logic, which we call , is strictly more
expressive than the other mu-calculi considered. It is also more expressive
than the temporal logic TCTL, while the other mu-calculi are incomparable with
TCTL in the setting of general timed automata
Type checking mCRL2
In this paper we present a type system for the data language of mCRL2, a process algebra based language for formalising the behaviour of communicating system. Much of the type system is standard, and follows the line of, e.g., Pierce [Pie02]. The data language that is described is rich, and supports (infinite) sets and bags, universal and existential quantification, and lambda abstraction. Recursive types can be defined using equational definitions. Subtyping is included for the full data language, and a coercion is given to transform a well-typed expression into a strictly typed expression.
A cure for stuttering parity games
We de¿ne governed stuttering bisimulation for parity games, weakening stuttering bisimulation by taking the ownership of vertices into account only when this might lead to observably different games. We show that governed stuttering bisimilarity is an equivalence for parity games and allows for a natural quotienting operation. Moreover, we prove that all pairs of vertices related by governed stuttering bisimilarity are won by the same player in the parity game. Thus, our equivalence can be used as a preprocessing step when solving parity games. Governed stuttering bisimilarity can be decided in O(n^2 m) time for parity games with n vertices and m edges. Our experiments indicate that governed stuttering bisimilarity is mostly competitive with stuttering equivalence on parity games encoding typical veri¿cation problems
Games for Bisimulations and Abstraction
Weak bisimulations are typically used in process algebras where silent steps
are used to abstract from internal behaviours. They facilitate relating
implementations to specifications. When an implementation fails to conform to
its specification, pinpointing the root cause can be challenging. In this paper
we provide a generic characterisation of branching-, delayed-, - and
weak-bisimulation as a game between Spoiler and Duplicator, offering an
operational understanding of the relations. We show how such games can be used
to assist in diagnosing non-conformance between implementation and
specification. Moreover, we show how these games can be extended to distinguish
divergences