351 research outputs found
Calculi for Synchrony and Asynchrony
AbstractA calculus for distributed computation is studied, based upon four combinators. A central idea is an Abelian group of actions which models the interfaces between components of a distributed computing agent. Using a notion of bisimulation, congruence relations are defined over computing agents, and thence an algebraic theory is derived. The calculus models both synchronous and asynchronous computation. In particular, it is shown that the author's Calculus of Communicating Systems (1980), which is an asynchronous model, is derivable from the calculus presented here
A Sequent Calculus for Modelling Interferences
A logic calculus is presented that is a conservative extension of linear
logic. The motivation beneath this work concerns lazy evaluation, true
concurrency and interferences in proof search. The calculus includes two new
connectives to deal with multisequent structures and has the cut-elimination
property. Extensions are proposed that give first results concerning our
objectives
Unifying type systems for mobile processes
We present a unifying framework for type systems for process calculi. The
core of the system provides an accurate correspondence between essentially
functional processes and linear logic proofs; fragments of this system
correspond to previously known connections between proofs and processes. We
show how the addition of extra logical axioms can widen the class of typeable
processes in exchange for the loss of some computational properties like
lock-freeness or termination, allowing us to see various well studied systems
(like i/o types, linearity, control) as instances of a general pattern. This
suggests unified methods for extending existing type systems with new features
while staying in a well structured environment and constitutes a step towards
the study of denotational semantics of processes using proof-theoretical
methods
Synchrony vs Causality in the Asynchronous Pi-Calculus
We study the relation between process calculi that differ in their either
synchronous or asynchronous interaction mechanism. Concretely, we are
interested in the conditions under which synchronous interaction can be
implemented using just asynchronous interactions in the pi-calculus. We assume
a number of minimal conditions referring to the work of Gorla: a "good"
encoding must be compositional and preserve and reflect computations,
deadlocks, divergence, and success. Under these conditions, we show that it is
not possible to encode synchronous interactions without introducing additional
causal dependencies in the translation.Comment: In Proceedings EXPRESS 2011, arXiv:1108.407
Synchrony versus causality in distributed systems
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugĂ€nglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Given a synchronous system, we study the question whether â or, under which conditions â the behaviour of that system can be realized by a (non-trivially) distributed and hence asynchronous implementation. In this paper, we partially answer this question by examining the role of causality for the implementation of synchrony in two fundamental different formalisms of concurrency, Petri nets and the Ï-calculus. For both formalisms it turns out that each âgoodâ encoding of synchronous interactions using just asynchronous interactions introduces causal dependencies in the translation
Multi-modal meaning â An empirically-founded process algebra approach
Humans communicate with different modalities. We offer an account of multi-modal meaning coordination, taking speech-gesture meaning coordination as a prototypical case. We argue that temporal synchrony (plus prosody) does not determine how to coordinate speech meaning and gesture meaning. Challenging cases are asynchrony and broadcasting cases, which are illustrated with empirical data. We propose that a process algebra account satisfies the desiderata. It models gesture and speech as independent but concurrent processes that can communicate flexibly with each other and exchange the same information more than once. The account utilizes the psi-calculus, allowing for agents, input-output-channels, concurrent processes, and data transport of typed lambda-terms. A multi-modal meaning is produced integrating speech meaning and gesture meaning into one semantic package. Two cases of meaning coordination are handled in some detail: the asynchrony between gesture and speech, and the broadcasting of gesture meaning across several dialogue contributions. This account can be generalized to other cases of multi-modal meaning
Process Algebras
Process Algebras are mathematically rigorous languages with well defined semantics that permit describing and verifying properties of concurrent communicating systems.
They can be seen as models of processes, regarded as agents that act and interact continuously with other similar agents and with their common environment. The agents may be real-world objects (even people), or they may be artifacts, embodied perhaps in computer hardware or software systems.
Many different approaches (operational, denotational, algebraic) are taken for describing the meaning of processes. However, the operational approach is the reference one. By relying on the so called Structural Operational Semantics (SOS), labelled transition systems are built and composed by using the different operators of the many different process algebras. Behavioral equivalences are used to abstract from unwanted details and identify those systems that react similarly to external
experiments
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