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πCalculus, Internal Mobility, and AgentPassing Calculi
 THEORETICAL COMPUTER SCIENCE
, 1995
"... The πcalculus is a process algebra which originates from CCS and permits a natural modelling of mobility (i.e., dynamic reconfigurations of the process linkage) using communication of names. Previous research has shown that the πcalculus has much greater expressiveness than CCS, but also a much mo ..."
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Cited by 80 (11 self)
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The πcalculus is a process algebra which originates from CCS and permits a natural modelling of mobility (i.e., dynamic reconfigurations of the process linkage) using communication of names. Previous research has shown that the πcalculus has much greater expressiveness than CCS, but also a much more complex mathematical theory. The primary goal of this work is to understand the reasons of this gap. Another goal is to compare the expressiveness of namepassing calculi, i.e., calculi like πcalculus where mobility is achieved via exchange of names, and that of agentpassing calculi, i.e., calculi where mobility is achieved via exchange of agents. We separate the mobility mechanisms of the πcalculus into two, respectively called internal mobility and external mobility. The study of the subcalculus which only uses internal mobility, called I, suggests that internal mobility is responsible for much of the expressiveness of the πcalculus, whereas external mobility is responsible for many of...
Algebraic Specification of Concurrent Systems
, 1999
"... State Machines" (ASM). 13.4.1 Evolving algebras (abstract state machines) The basic idea of the "evolving algebras" (see, for instance, [Gur93,Gur95]) is perfectly summarized by their name. Essentially an evolving algebra (specification) consists of a description of a (nonlabeled) transition system ..."
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State Machines" (ASM). 13.4.1 Evolving algebras (abstract state machines) The basic idea of the "evolving algebras" (see, for instance, [Gur93,Gur95]) is perfectly summarized by their name. Essentially an evolving algebra (specification) consists of a description of a (nonlabeled) transition system, whose states are algebras on the same homogeneous signature built over the same universe (including Boolean values). Some of the operation symbols are qualified as "static" and their interpretation is the same in any (algebra which is a) state. The transitions are defined by rules of the following form: econd ) up 1 ; : : : up k where, for each j = 1; : : : ; k, the function update up j has form f j (e j 1 ; : : : ; e j n j ) := e j ; econd, e 1 1 , : : : , e 1 n1 , e 1 , : : : , e k 1 , : : : , e k nk , e k are "descriptions" (any possible mathematically intelligible expressions) of elements of the universe, the first describing a Boolean value, and for j = 1; : : : ; ...
Modular Specification of Concurrent Systems With Observational Logic
 in J.L. Fiadeiro (ed.) Recent Developments in Algebraic Development Techniques
, 1999
"... . We present a dynamic form of observational logic for specifying concurrent systems on the basis of their observable behaviour, in particular without needing a language for describing states, which are regarded as nonobservable. The logic is based on quantales. The models are labelled transition s ..."
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. We present a dynamic form of observational logic for specifying concurrent systems on the basis of their observable behaviour, in particular without needing a language for describing states, which are regarded as nonobservable. The logic is based on quantales. The models are labelled transition systems, and a weakly complete proof system is presented. We study the logic from the point of view of modularity; vertical modularity is based on a notion of implementation of systems and refinement of specifications, and horizontal modularity is based on parallel composition of systems and specifications. Several compositionality results are presented. As an example we see a specification of a stack and its implementation over an array and a pointer. 1 Introduction This paper introduces a logic for specifying concurrent systems on the basis of their observable behaviour, in particular without needing a language for describing states, which are regarded as nonobservable and ultimately phys...
Equivalence semantics for concurrency: comparison and application
, 1998
"... Since the development of CCS and other process algebras, many extensions to these process algebras have been proposed to model different aspects of concurrent computation. It is important both theoretically and practically to understand the relationships between these process algebras and between ..."
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Cited by 3 (2 self)
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Since the development of CCS and other process algebras, many extensions to these process algebras have been proposed to model different aspects of concurrent computation. It is important both theoretically and practically to understand the relationships between these process algebras and between the semantic equivalences that are defined for them. In this thesis, I investigate the comparison of semantic equivalences based on bisimulation which are defined for process algebras whose behaviours are described by structured operational semantics, and expressed as labelled transition systems. I first consider a hierarchy of bisimulations for extensions to CCS, using both existing and new results to describe the relationships between their equivalences with respect to pure CCS terms. I then consider a more general approach to comparison by investigating labelled transition systems with structured labels. I define bisimulation homomorphisms between labelled transition systems with different labels, and show how these can be used to compare equivalences. Next, I work in the metatheory of process algebras and consider a new format that is an extension of the tyft/tyxt format for transition system specifications. This format treats labels syntactically instead of schematically, and hence I use a definition of bisimulation which requires equivalence between labels instead of exact matching. I show that standard results such as congruence and conservative extension hold for the new format. I then investigate how comparison of equivalences can be approached through the notion of extension to transition system specifications. This leads to the main results of this study which show how in a very general fashion the bisimulations defined for two different process algebras can be compared over a subset of terms of the process algebras. I also consider what implications the conditions which are required to obtain these results have for modelling process algebras, and show that these conditions do not impose significant limitations. Finally, I show how these results can be applied to existing process algebras. I model a number of process algebras with the extended format and derive new results from the metatheory developed. ii
Algebraic System Specification and Development: Survey and Annotated Bibliography  Second Edition 
, 1997
"... Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.5.4 Special Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.6 Semantics of Programming Languages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.6.1 Semantics of Ada . . . ..."
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Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.5.4 Special Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.6 Semantics of Programming Languages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.6.1 Semantics of Ada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.6.2 Action Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.7 Specification Languages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.7.1 Early Algebraic Specification Languages . . . . . . . . . . . . . . . . . . . . . . . . 53 4.7.2 Recent Algebraic Specification Languages . . . . . . . . . . . . . . . . . . . . . . . 55 4.7.3 The Common Framework Initiative. . . . . . . . . . . . . . . . . . . . . . . . . . . 56 5 Methodology 57 5.1 Development Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 5.1.1 Applica...