We present the a-calculus, a calculus of communicating systems in which one can naturally express processes which have changing structure. Not only may the component agents of a system be arbitrarily linked, but a communication between neighbours may carry information which changes that linkage. The calculus is an extension of the process algebra CCS, following work by Engberg and Nielsen, who added mobility to CCS while preserving its algebraic properties. The rr-calculus gains simplicity by removing all distinction between variables and constants; communication links are identified by names, and computation is represented purely as the communication of names across links. After an illustrated description of how the n-calculus generalises conventional process algebras in treating mobility, several examples exploiting mobility are given in some detail. The important examples are the encoding into the n-calculus of higher-order functions (the I-calculus and combinatory algebra), the transmission of processes as values, and the representation of data structures as processes. The paper continues by presenting the algebraic theory of strong bisimilarity and strong equivalence, including a new notion of equivalence indexed by distinctions-i.e., assumptions of inequality among names. These theories are based upon a semantics in terms of a labeled transition system and a notion of strong bisimulation, both of which are expounded in detail in a companion paper. We also report briefly on work-in-progress based upon the corresponding notion of weak bisimulation, in which internal actions cannot be observed. 0 1992 Academic Press, Inc.

A calculus of mobile processes, II

An Introduction to MultiAgent Systems.

From the Publisher:
Since the introduction of Hoares' Communicating Sequential Processes notation, powerful new tools have transformed CSP into a practical way of describing industrial-sized problems. This book gives you the fundamental grasp of CSP concepts you'll need to take advantage of those tools.Part I provides a detailed foundation for working with CSP, using as little mathematics as possible. It introduces the ideas behind operational, denotational and algebraic models of CSP. Parts II and III go into greater detail about theory and practice. Topics include: parallel operators, hiding and renaming, piping and enslavement, buffers and communication, termination and sequencing, and semantic theory. Three detailed practical case studies are also presented.For anyone interested in modeling sequential processes.

/pdf/the-theory-and-practice-of-concurrency-1kzi2sg7cs.pdf

The Theory and Practice of Concurrency

Publisher Summary
This chapter focuses on rewrite systems, which are directed equations used to compute by repeatedly replacing sub-terms of a given formula with equal terms until the simplest form possible is obtained. As a formalism, rewrite systems have the full power of Turing machines and may be thought of as nondeterministic Markov algorithms over terms rather than strings. The theory of rewriting is in essence a theory of normal forms. To some extent, it is an outgrowth of the study of A. Church's Lambda Calculus and H. B. Curry's Combinatory Logic. The chapter discusses the syntax and semantics of equations from the algebraic, logical, and operational points of view. To use a rewrite system as a decision procedure, it must be convergent. The chapter describes this fundamental concept as an abstract property of binary relations. To use a rewrite system for computation or as a decision procedure for validity of identities, the termination property is crucial. The chapter presents the basic methods for proving termination. The chapter discusses the question of satisfiability of equations and the convergence property applied to rewriting.

CHAPTER 6 – Rewrite Systems

We survey the literature available on the topic of domain-specific languages as used for the construction and maintenance of software systems. We list a selection of 75 key publications in the area, and provide a summary for each of the papers. Moreover, we discuss terminology, risks and benefits, example domain-specific languages, design methodologies, and implementation techniques.

https://people.cis.ksu.edu/~schmidt/505f14/Lectures/DSLbib.pdf

Domain-specific languages: an annotated bibliography

11 Extension of process algebra In this paper we extend process algebra with a new operator that will be helpful to describe process creation From a methodological point of view the extension of process algebra with new operators is just the right way to incorporate new features Only in a very rich calculus with many operators one may hope to be able to perform significant algebraic calculations on systems In many cases a new feature requires new (additional) syntax and more equations, only in very rare circumstances the addition of equations alone suffices to obtain an appropriate model of some new system aspect The core system ACP, see [4,5,6], describes asynchronous cooperation with synchronous communication

/pdf/a-process-creation-mechanism-in-process-algebra-4b2e38a81i.pdf

A process creation mechanism in process algebra

We study sequential programs that are instruction sequences with jump-shift instructions in the setting of PGA (ProGram Algebra). Jump-shift instructions preceding a jump instruction increase the position to jump to. The jump-shift instruction is not found in programming practice. Its merit is that the expressive power of PGA extended with the jump-shift instruction, is not reduced if the reach of jump instructions is bounded. This is used to show that there exists a finite-state execution mechanism that by making use of a counter can produce each finite-state thread from some program that is a finite or periodic infinite sequence of instructions from a finite set.

Program Algebra with a Jump-Shift Instruction

Process Algebra Primitives for File Transfer

Abstract We consider the completeness of Hoare's logic with a first-order assertion language applied to while-programs containing variables of two (or more) distinct types. Whilst Cook's completeness theorem generalizes to many-sorted interpretations, certain fundamentally important structures turn out not to be expressive. We study the case of programs with distinguished counter variables and Boolean variables adjoined; for example, we show that adding counters to arithmetic destroys expressiveness.

Hoare's logic for programming languages with two data types : (preprint)

Control code is a concept that is closely related to a frequently occurring practitioner's view on what is a program: code that is capable of controlling the behaviour of some machine. We present a logical approach to explain issues concerning control codes that are independent of the details of the behaviours that are controlled. Using this approach, such issues can be explained at a very abstract level. We illustrate this among other things by means of an example about the production of a new compiler from an existing one. The approach is based on abstract machine models, called machine structures. We introduce a model of systems that provide execution environments for the executable codes of machine structures and use it to go into portability of control codes.

Jan A. Bergstra

Papers

A process creation mechanism in process algebra

Program Algebra with a Jump-Shift Instruction

Process Algebra Primitives for File Transfer

Hoare's logic for programming languages with two data types : (preprint)

Machine structure oriented control code logic