15,176 research outputs found
Fairness of components in system computations
In this paper we provide a simple characterization of (weak) fairness of components as defined by Costa and Stirling. The study is carried out at system specification level by resorting to a common process description language. This paper follows and exploits similar techniques as those developed in an earlier paper -- where fairness of actions was taken into account and was contrasted to the PAFAS timed operational semantics -- but the characterization of fair executions is based on a new semantics for PAFAS; it makes use of only two copies of each basic action instead of infinitely many and allows for a simple and finite representation of fair executions by using regular expressions. The new semantics can also be understood as describing timed behaviour of systems with upper time bounds. The paper discusses in detail how this new semantics differs from the old one, and why theses changes are necessary to properly capture fairness of components
Explicit fairness in testing semantics
In this paper we investigate fair computations in the pi-calculus. Following
Costa and Stirling's approach for CCS-like languages, we consider a method to
label process actions in order to filter out unfair computations. We contrast
the existing fair-testing notion with those that naturally arise by imposing
weak and strong fairness. This comparison provides insight about the
expressiveness of the various `fair' testing semantics and about their
discriminating power.Comment: 27 pages, 1 figure, appeared in LMC
PLTL Partitioned Model Checking for Reactive Systems under Fairness Assumptions
We are interested in verifying dynamic properties of finite state reactive
systems under fairness assumptions by model checking. The systems we want to
verify are specified through a top-down refinement process. In order to deal
with the state explosion problem, we have proposed in previous works to
partition the reachability graph, and to perform the verification on each part
separately. Moreover, we have defined a class, called Bmod, of dynamic
properties that are verifiable by parts, whatever the partition. We decide if a
property P belongs to Bmod by looking at the form of the Buchi automaton that
accepts the negation of P. However, when a property P belongs to Bmod, the
property f => P, where f is a fairness assumption, does not necessarily belong
to Bmod. In this paper, we propose to use the refinement process in order to
build the parts on which the verification has to be performed. We then show
that with such a partition, if a property P is verifiable by parts and if f is
the expression of the fairness assumptions on a system, then the property f =>
P is still verifiable by parts. This approach is illustrated by its application
to the chip card protocol T=1 using the B engineering design language
Verification and Synthesis of Symmetric Uni-Rings for Leads-To Properties
This paper investigates the verification and synthesis of parameterized
protocols that satisfy leadsto properties on symmetric
unidirectional rings (a.k.a. uni-rings) of deterministic and constant-space
processes under no fairness and interleaving semantics, where and are
global state predicates. First, we show that verifying for
parameterized protocols on symmetric uni-rings is undecidable, even for
deterministic and constant-space processes, and conjunctive state predicates.
Then, we show that surprisingly synthesizing symmetric uni-ring protocols that
satisfy is actually decidable. We identify necessary and
sufficient conditions for the decidability of synthesis based on which we
devise a sound and complete polynomial-time algorithm that takes the predicates
and , and automatically generates a parameterized protocol that
satisfies for unbounded (but finite) ring sizes. Moreover, we
present some decidability results for cases where leadsto is required from
multiple distinct predicates to different predicates. To demonstrate
the practicality of our synthesis method, we synthesize some parameterized
protocols, including agreement and parity protocols
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