104 research outputs found
The Largest Respectful Function
Respectful functions were introduced by Sangiorgi as a compositional tool to
formulate short and clear bisimulation proofs. Usually, the larger the
respectful function, the easier the bisimulation proof. In particular the
largest respectful function, defined as the pointwise union of all respectful
functions, has been shown to be very useful. We here provide an explicit and
constructive characterization of it
Priorities Without Priorities: Representing Preemption in Psi-Calculi
Psi-calculi is a parametric framework for extensions of the pi-calculus with
data terms and arbitrary logics. In this framework there is no direct way to
represent action priorities, where an action can execute only if all other
enabled actions have lower priority. We here demonstrate that the psi-calculi
parameters can be chosen such that the effect of action priorities can be
encoded.
To accomplish this we define an extension of psi-calculi with action
priorities, and show that for every calculus in the extended framework there is
a corresponding ordinary psi-calculus, without priorities, and a translation
between them that satisfies strong operational correspondence. This is a
significantly stronger result than for most encodings between process calculi
in the literature.
We also formally prove in Nominal Isabelle that the standard congruence and
structural laws about strong bisimulation hold in psi-calculi extended with
priorities.Comment: In Proceedings EXPRESS/SOS 2014, arXiv:1408.127
Expressiveness of Process Algebras
AbstractWe examine ways to measure expressiveness of process algebras, and recapitulate and compare some related results from the literature
Structural and Behavioural Equivalences of Networks
We define an algebraic language for networks of synchronously communicating
processes. A node in the Network may have several ports; a port is either
external to the whole network or connected through a link to another
port. The language contains two types of operations: parallel composition
of two networks, and interlinking of two external ports within a network.
We interpret this language in two ways: first we give a structural
semantics, where terms are mapped to graphs representing the structure of
networks, and second we give a behavioural semantics, where terms are
mapped to behaviour schemes. A schema corresponds to a behaviour
parameterised on the behaviours of the network nodes. These semantics give
rise to structural and behavioural equivalences.
We compare the equivalences and give sound and complete axiomatisations
An algebraic verification of a mobile network
In a mobile communication network some nodes change location, and are therefore connected to different other nodes at different points in time. We show how such a network can be formally defined and verified using the p-calculus, which is a development of CCS (Calculus of Communicating Systems) allowing port names to be sent as parameters in communication events. An example of a mobile network is the Public Land Mobile Network currently being developed by the European Telecommunication Standards Institute. We concentrate on the handover procedures which controls the dynamic topology of the network
Motivation and Grade Gap Related to Gender in a Programming Course
In a programming course at Uppsala University, Sweden, there has been a significant difference between the average grade of female students and that of their male counterparts. This work in progress presents some results and potential solutions related to this problem, and makes them explicit
Deciding bisimulation equivalences for a class of non-finite-state programs
Traditionally, many automatic program verification techniques are applicable only to finite-state programs. In this paper we show how to extend some verification techniques to infinite-state programs that may read, store, and write data but not perform any other computations. We present algorithms for deciding strong equivalence and observation equivalence, defined by bisimulations (as in CCS), between such programs. These algorithms have major applications in verification of communication protocols. The equivalence problems are shown to be NP-hard in the size of the programs
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