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117
Equivalences of Statecharts
, 1996
"... . We present a new semantics of Statecharts that excludes failures and a compositional formulation of this semantics based on Labelled Transition Systems (LTS). We consider a hierarchy of LTS equivalences and we study their congruence properties w.r. to statechart operators. 1 ..."
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Cited by 36 (4 self)
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. We present a new semantics of Statecharts that excludes failures and a compositional formulation of this semantics based on Labelled Transition Systems (LTS). We consider a hierarchy of LTS equivalences and we study their congruence properties w.r. to statechart operators. 1
A framework based on implementation relations for implementing LOTOS specifications
, 1992
"... A framework is developed for studying the implementation process, as a stepwise process in which an abstract specification is successively transformed to reach a final compilable specification adapted to the computer environment. In this context, an implementation relation is referred to as the rela ..."
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Cited by 27 (2 self)
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A framework is developed for studying the implementation process, as a stepwise process in which an abstract specification is successively transformed to reach a final compilable specification adapted to the computer environment. In this context, an implementation relation is referred to as the relation which should link any "valid" implementation to its abstract formal specification. In other words, the implementation relation is intended to express formally the notion of validity. Our framework allows the exact characterization of the transformations which may take place at each step for a given implementation relation. This framework is essential for dealing with nontransitive implementation relations. In the second part of the paper, these results are exemplified in LOTOS on some existing relations, and an apparent paradox is presented. Some new results about these relations are also derived. Keywords LOTOS, implementation relation, refinement, implementation process, transforma...
Formal Object Oriented Development of Software Systems using LOTOS
, 1993
"... Formal methods are necessary in achieving correct software: that is, software that can be proven to fulfil its requirements. Formal specifications are unambiguous and analysable. Building a formal model improves understanding. The modelling of nondeterminism, and its subsequent removal in formal ste ..."
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Cited by 25 (14 self)
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Formal methods are necessary in achieving correct software: that is, software that can be proven to fulfil its requirements. Formal specifications are unambiguous and analysable. Building a formal model improves understanding. The modelling of nondeterminism, and its subsequent removal in formal steps, allows design and implementation decisions to be made when most suitable. Formal models are amenable to mathematical manipulation and reasoning, and facilitate rigorous testing procedures. However, formal methods are not widely used in software development. In most cases, this is because they are not suitably supported with development tools. Further, many software developers do not recognise the need for rigour. Object oriented techniques are successful in the production of large, complex software systems. The methods are based on simple mathematical models of abstraction and classification. Further, the object oriented approach offers a conceptual consistency across all stages of soft...
Basic Observables for Processes
 Information and Computation
, 1999
"... A general approach for defining behavioural preorders over process terms as the maximal precongruences induced by basic observables is examined. Three different observables, that provide information about the initial communication capabilities of processes and about the possibility that processes ..."
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Cited by 23 (6 self)
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A general approach for defining behavioural preorders over process terms as the maximal precongruences induced by basic observables is examined. Three different observables, that provide information about the initial communication capabilities of processes and about the possibility that processes get engaged in divergent computations, will be considered. We show that the precongruences induced by our basic observables coincide with intuitive and/or widely studied behavioural preorders. In particular, we retrieve in our setting the must preorder of De Nicola and Hennessy and the fair/should preorder introduced by Cleaveland and Natarajan and by Brinksma, Rensink and Vogler. A new form of testing preorder, which we call safemust, also emerges. The alternative characterizations we offer shed light on the differences between these preorders, and on the role played in their definition by tests for divergence. 1 Introduction In the classical theory of functional programming, the point...
Contract Compliance and Choreography Conformance in the Presence of Message Queues
"... Choreography conformance and contract compliance have been widely studied in the context of synchronous communication. In this paper we approach a more realistic scenario in which the messages containing the invocations are queued in the called service. More precisely, we study the foundational aspe ..."
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Cited by 17 (4 self)
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Choreography conformance and contract compliance have been widely studied in the context of synchronous communication. In this paper we approach a more realistic scenario in which the messages containing the invocations are queued in the called service. More precisely, we study the foundational aspects of contract compliance in a language independent way by just taking contracts to be finite labeled transition systems. Then, we relate the proposed theory of contract compliance with choreography specifications à la WSCDL where activities are interpreted as pairs of send and receive events. An interesting consequence of adopting a language independent representation of contracts is that choreography projection can be defined in structured operational semantics.
Modeling Systems by Probabilistic Process Algebra: An Event Structures Approach
, 1993
"... This paper treats a probabilistic version of (a subset of) the process algebra LOTOS. It incorporates a probabilistic choice assigning a probability of occurrence to each of its alternatives. Opposed to the traditional interleaving semantics used for existing probabilistic process algebras the prese ..."
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Cited by 14 (6 self)
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This paper treats a probabilistic version of (a subset of) the process algebra LOTOS. It incorporates a probabilistic choice assigning a probability of occurrence to each of its alternatives. Opposed to the traditional interleaving semantics used for existing probabilistic process algebras the presented language is based on a true concurrency semantics. This enables us to distinguish between nondeterminism and parallelism, to reduce the state explosion problem and, moreover, to analyse part of the system without considering other (irrelevant) parts. In this paper the language is presented and the formal semantics is defined by using an extension of bundle event structures. A short example illustrates the novelties of the language and links the language to stochastic analysis based on semiMarkov chains.
Flat Fragments of CTL and CTL*: Separating the Expressive and Distinguishing Powers
"... We study both the expressive and the distinguishing powers of at temporal logics. These are fragments obtained by restricting the rst argument of the Until operator to propositional formulae. Both the lineartime and the branchingtime cases are considered. Keywords: temporal logic, LTL, CTL, expre ..."
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Cited by 14 (0 self)
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We study both the expressive and the distinguishing powers of at temporal logics. These are fragments obtained by restricting the rst argument of the Until operator to propositional formulae. Both the lineartime and the branchingtime cases are considered. Keywords: temporal logic, LTL, CTL, expressiveness, bisimulation 1 Introduction Temporal logic lies at the basis of several specication formalisms that are widely used in practice. For a large part, this acceptance stems from the availability of software tools for automated verication, that allow to prove or disprove the satisfaction of a temporal property interpreted over a model of the system under consideration. Model checking is such an approach, that has proven successful in the debugging and verication of hardware circuitry and communication protocols for example. Being based on an exhaustive inspection of the state space of the model, the scalability of model checking is limited, which is referred to as the state expl...
An Algebraic Theory of Process Efficiency
 In LICS ’96
, 1996
"... This paper presents a testingbased semantic theory for reasoning about the efficiency of concurrent systems as measured in terms of the amount of their internal activity. The semantic preorders are given an algebraic characterization, and their optimality is established by means of a full abstractn ..."
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Cited by 12 (1 self)
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This paper presents a testingbased semantic theory for reasoning about the efficiency of concurrent systems as measured in terms of the amount of their internal activity. The semantic preorders are given an algebraic characterization, and their optimality is established by means of a full abstractness result. They are also shown to subsume existing bisimulationbased efficiency preorders. An example is provided to illustrate the utility of this approach. 1. Introduction Process algebras [12, 10, 3] have attracted substantial attention over the past decade and a half as frameworks for system verification. A hallmark of these theories is the development of behavioral equivalences and preorders that relate systems on the basis of their extensional behavior. In these frameworks, specifications are usually given as "highlevel " systems; to prove a system meets such a specification, one shows that they are related appropriately by such a behavioral relation. When the behavioral relation is...
Split and ST bisimulation semantics
 Information and Computation
"... In this paper the notion of action atomicity is relaxed by permitting actions to be observed in the middle of their evolution. Non atomic semantic equivalences, based on the notion of bisimulation, are studied over stable event structures. Splitn bisimulation equivalence (denoted n ¸) considers ea ..."
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Cited by 12 (3 self)
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In this paper the notion of action atomicity is relaxed by permitting actions to be observed in the middle of their evolution. Non atomic semantic equivalences, based on the notion of bisimulation, are studied over stable event structures. Splitn bisimulation equivalence (denoted n ¸) considers each event as composed of n phases. ST bisimulation equivalence (denoted ST ¸ ) is a slight refinement of 2 ¸ where each ending phase is unambiguously associated to a beginning phase. We prove that, by increasing n, we get finer and finer equivalences (i.e. n+1 ¸ ` n ¸) and, moreover, that n+1 ¸ coincides with ST ¸ over those event structures whose autoconcurrency is at most n. The main consequence of these results is that, for image finite event structures, ST ¸ is the intersection of all the n ¸. 1 Introduction Most of the behavioural equivalences for concurrent systems are usually based on the assumption that the execution of an action is an atomic activity which cannot b...