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

Modal Logics for Nominal Transition Systems

We define a uniform semantic substrate for a wide variety of process calculi where states and action labels can be from arbitrary nominal sets. A Hennessy-Milner logic for these systems is introduced, and proved adequate for bisimulation equivalence. A main novelty is the use of finitely supported infinite conjunctions. We show how to treat different bisimulation variants such as early, late and open in a systematic way, and make substantial comparisons with related work. The main definitions and theorems have been formalized in Nominal Isabelle