80 research outputs found
On the decidability of fragments of the asynchronous π-calculus
AbstractWe study the decidability of a reachability problem for various fragments of the asynchronous π-calculus. We consider the combination of three main features: name generation, name mobility, and unbounded control. We show that the combination of name generation with either name mobility or unbounded control leads to an undecidable fragment. On the other hand, we prove that name generation without name mobility and with bounded control is decidable by reduction to the coverability problem for Petri Nets
On the Axiomatisation of Branching Bisimulation Congruence over CCS
In this paper we investigate the equational theory of (the restriction, relabelling, and recursion free fragment of) CCS modulo rooted branching bisimilarity, which is a classic, bisimulation-based notion of equivalence that abstracts from internal computational steps in process behaviour. Firstly, we show that CCS is not finitely based modulo the considered congruence. As a key step of independent interest in the proof of that negative result, we prove that each CCS process has a unique parallel decomposition into indecomposable processes modulo branching bisimilarity. As a second main contribution, we show that, when the set of actions is finite, rooted branching bisimilarity has a finite equational basis over CCS enriched with the left merge and communication merge operators from ACP
Introduction to the ISO specification language LOTOS
LOTOS is a specification language that has been specifically developed for the formal description of the OSI (Open Systems Interconnection) architecture, although it is applicable to distributed, concurrent systems in general. In LOTOS a system is seen as a set of processes which interact and exchange data with each other and with their environment. LOTOS is expected to become an ISO international standard by 1988
A theory of processes with durational actions
AbstractA new bisimulation based semantics, called performance equivalence, is proposed for a process algebra equipped with the TCSP parallel operator. This semantics relies on the basic assumption that actions are time-consuming, where their duration is statically fixed. Performance equivalence equates systems whenever they perform the same actions in the same amount of time, thus introducing a simple form of performance evaluation in process algebras. A comparison with other equivalences is provided; in particular, we show that performance equivalence is strictly finer than step bisimulation equivalence and strictly coarser than partial ordering bisimulation equivalence
Recursion vs Replication in Process Calculi: Expressiveness
International audienceIn this paper we shall survey and discuss in detail the work on the relative expressiveness of recursion and replication in various process calculi. Namely, CCS, the pi-calculus, and the Ambient calculus. We shall give evidence that the ability of expressing recursive behaviour via replication often depends on the scoping mechanisms of the given calculus which compensate for the restriction of replication
Expressiveness of Recursion, Replication and Scope Mechanisms in Process Calculi
International audienceIn this paper we shall survey and discuss in detail the work on the relative expressiveness of recursion and replication in various process calculi. Namely, CCS, the pi-calculus, the Ambient calculus, Concurrent Constraint Programming and calculi for Cryptographic Protocols. We shall give evidence that the ability of expressing recursive behaviour via replication often depends on the scoping mechanisms of the given calculus which compensate for the restriction of replication
Curry-style type Isomorphisms and Game Semantics
Curry-style system F, ie. system F with no explicit types in terms, can be
seen as a core presentation of polymorphism from the point of view of
programming languages. This paper gives a characterisation of type isomorphisms
for this language, by using a game model whose intuitions come both from the
syntax and from the game semantics universe. The model is composed of: an
untyped part to interpret terms, a notion of game to interpret types, and a
typed part to express the fact that an untyped strategy plays on a game. By
analysing isomorphisms in the model, we prove that the equational system
corresponding to type isomorphisms for Curry-style system F is the extension of
the equational system for Church-style isomorphisms with a new, non-trivial
equation: forall X.A = A[forall Y.Y/X] if X appears only positively in A.Comment: Accept\'e \`a Mathematical Structures for Computer Science, Special
Issue on Type Isomorphism
A Formal Approach to Open Multiparty Interactions
We present a process algebra aimed at describing interactions that are
multiparty, i.e. that may involve more than two processes and that are open,
i.e. the number of the processes they involve is not fixed or known a priori.
Here we focus on the theory of a core version of a process calculus, without
message passing, called Core Network Algebra (CNA). In CNA communication
actions are given not in terms of channels but in terms of chains of links that
record the source and the target ends of each hop of interactions. The
operational semantics of our calculus mildly extends the one of CCS. The
abstract semantics is given in the style of bisimulation but requires some
ingenuity. Remarkably, the abstract semantics is a congruence for all operators
of CNA and also with respect to substitutions, which is not the case for strong
bisimilarity in CCS. As a motivating and running example, we illustrate the
model of a simple software defined network infrastructure.Comment: 62 page
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