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Fair testing
 Concur ’95: Concurrency Theory, volume 962 of Lecture Notes in Computer Science
, 1995
"... In this paper we present a solution to the longstanding problem of characterising the coarsest livenesspreserving precongruence with respect to a full (TCSPinspired) process algebra. In fact, we present two distinct characterisations, which give rise to the same relation: an operational one base ..."
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Cited by 58 (0 self)
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In this paper we present a solution to the longstanding problem of characterising the coarsest livenesspreserving precongruence with respect to a full (TCSPinspired) process algebra. In fact, we present two distinct characterisations, which give rise to the same relation: an operational one based on a De NicolaHennessylike testing modality which we call shouldtesting, and a denotational one based on a refined notion of failures. One of the distinguishing characteristics of the shouldtesting precongruence is that it abstracts from divergences in the same way as Milner’s observation congruence, and as a consequence is strictly coarser than observation congruence. In other words, shouldtesting has a builtin fairness assumption. This is in itself a property long soughtafter; it is in notable contrast to the wellknown musttesting of De Nicola and Hennessy (denotationally characterised by a combination of failures and divergences), which treats divergence as catrastrophic and hence is incompatible with observation congruence. Due to these characteristics, shouldtesting supports modular reasoning and allows to use the proof techniques of observation congruence, but also supports additional laws and techniques.
Trace and Testing Equivalence on Asynchronous Processes
 Information and Computation
, 1999
"... We study trace and maytesting equivalences in the asynchronous versions of CCS and calculus. We start from the operational definition of the maytesting preorder and provide for it finitary and fully abstract tracebased characterizations, along with a complete inequational proof system. We also ..."
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Cited by 32 (1 self)
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We study trace and maytesting equivalences in the asynchronous versions of CCS and calculus. We start from the operational definition of the maytesting preorder and provide for it finitary and fully abstract tracebased characterizations, along with a complete inequational proof system. We also touch upon two variants of this theory, by first considering a more demanding equivalence notion (musttesting) and then a richer version of asynchronous CCS. The results throw light on the difference between synchronous and asynchronous communication and on the weaker testing power of asynchronous observations. Keywords: Asynchronous Communications, Process Algebras, Semantics. This paper is an extended and revised version of [8] and [9]. 1 Contents 1 Introduction 3 2 Asynchronous CCS 5 2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Operational semantics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Maytesting semant...
Testing Theories for Asynchronous Languages
 In the Proc. of FSTTCS'98, LNCS 1530
, 1998
"... We study testing preorders for an asynchronous version of CCS called TACCS, where message emission is non blocking. We first give a labelled transition system semantics for this language, which includes both external and internal choice operators. By applying the standard denitions of may and must t ..."
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Cited by 20 (1 self)
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We study testing preorders for an asynchronous version of CCS called TACCS, where message emission is non blocking. We first give a labelled transition system semantics for this language, which includes both external and internal choice operators. By applying the standard denitions of may and must testing to this semantics we obtain two behavioural preorders based on asynchronous observations, ! and . We present alternative behavioural characterisations of these preorders, which are subsequently used to obtain equational theories for the finite fragment of the language.
Basic Observables for a Calculus for Global Computing
, 2004
"... We discuss a basic process calculus useful for modelling applications over global computing systems and present the associated semantic theories as determined by some basic notions of observation. The main features of the calculus are explicit distribution, remote operations, process mobility and ..."
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Cited by 17 (6 self)
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We discuss a basic process calculus useful for modelling applications over global computing systems and present the associated semantic theories as determined by some basic notions of observation. The main features of the calculus are explicit distribution, remote operations, process mobility and asynchronous communication through distributed data spaces. We introduce some natural notions of extensional observations and study their closure under operational reductions and/or language contexts to obtain barbed congruence and may testing. For these equivalences, we provide alternative tractable characterizations as labelled bisimulation and trace equivalence. We discuss some of the induced equational laws and relate them to design choices of the calculus. In particular, we show that some of these laws do not hold any longer if the language is rendered less abstract by introducing (asynchronous and undetectable) failures or by implementing remote communications via process migrations and local exchanges. In both
Branching vs. linear time – semantical perspective
 In Proc. 5th Int’l Symp. on ATVA, LNCS 4762
"... Abstract. The discussion in the computerscience literature of the relative merits of linear versus branchingtime frameworks goes back to early 1980s. One of the beliefs dominating this discussion has been that the lineartime framework is not expressive enough semantically, making lineartime log ..."
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Cited by 12 (2 self)
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Abstract. The discussion in the computerscience literature of the relative merits of linear versus branchingtime frameworks goes back to early 1980s. One of the beliefs dominating this discussion has been that the lineartime framework is not expressive enough semantically, making lineartime logics lacking in expressiveness. In this work we examine the branchinglinear issue from the perspective of process equivalence, which is one of the most fundamental notions in concurrency theory, as defining a notion of process equivalence essentially amounts to defining semantics for processes. Over the last three decades numerous notions of process equivalence have been proposed. Researchers in this area do not anymore try to identify the “right ” notion of equivalence. Rather, focus has shifted to providing taxonomic frameworks, such as “the linearbranching spectrum”, for the many proposed notions and trying to determine suitability for different applications. We revisit this issue here from a fresh perspective. We postulate three principles that we view as fundamental to any discussion of process equivalence. First, we borrow from research in denotational semantics and take contextual equivalence as the primary notion of equivalence. This eliminates many testing scenarios as either too strong or too weak. Second, we require the description of a process to fully specify all relevant behavioral aspects of the process. Finally, we require observable process behavior to be reflected in its input/output behavior. Under these postulates the distinctions between the linear and branching semantics tend to evaporate. As an example, we apply these principles to the framework of transducers, a classical notion of statebased processes that dates back to the 1950s and is well suited to hardware modeling. We show that our postulates result in a unique notion of process equivalence, which is trace based, rather than tree based. 1
A hybrid type system for lockfreedom of mobile processes
, 2008
"... We propose a type system for lockfreedom in the πcalculus, which guarantees that certain communications will eventually succeed. Distinguishing features of our type system are: it can verify lockfreedom of concurrent programs that have sophisticated recursive communication structures; it can be ..."
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Cited by 5 (0 self)
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We propose a type system for lockfreedom in the πcalculus, which guarantees that certain communications will eventually succeed. Distinguishing features of our type system are: it can verify lockfreedom of concurrent programs that have sophisticated recursive communication structures; it can be fully automated; it is hybrid, in that it combines a type system for lockfreedom with local reasoning about deadlockfreedom, termination, and confluence analyses. Moreover, the type system is parameterized by deadlockfreedom/termination/confluence analyses, so that any methods (e.g. type systems and model checking) can be used for those analyses. A lockfreedom analysis tool has been implemented based on the proposed type system, and tested for nontrivial programs.
Encoding asynchronous interactions using open Petri nets
"... We present an encoding for (bound) processes of the asynchronous CCS with replication into open Petri nets: ordinary Petri nets equipped with a distinguished set of open places. The standard token game of nets models the reduction semantics of the calculus; the exchange of tokens on open places mode ..."
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Cited by 4 (1 self)
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We present an encoding for (bound) processes of the asynchronous CCS with replication into open Petri nets: ordinary Petri nets equipped with a distinguished set of open places. The standard token game of nets models the reduction semantics of the calculus; the exchange of tokens on open places models the interactions between processes and their environment. The encoding preserves strong and weak CCS asynchronous bisimilarities: it thus represents a relevant step in establishing a precise correspondence between asynchronous calculi and (open) Petri nets. The work is intended as fostering the technology transfer between these formalisms: as an example, we discuss how some results on expressiveness can be transferred from the calculus to nets and back.
A Semantic Theory for Global Computing Systems
, 2004
"... We introduce cKlaim, a process calculus that can be thought of as a variant of the #calculus with process distribution, process mobility and asynchronous communication through distributed repositories. Upon it, we develop a semantic theory to reason about programs. More precisely, we introduce a ..."
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Cited by 4 (2 self)
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We introduce cKlaim, a process calculus that can be thought of as a variant of the #calculus with process distribution, process mobility and asynchronous communication through distributed repositories. Upon it, we develop a semantic theory to reason about programs. More precisely, we introduce a natural contextually defined behavioural semantics, give a coinductive characterization in terms of a labelled bisimulation and illustrate some significant laws. Then, we smoothly tune the theory to model two more concrete settings obtained by explicitly considering failures and node connections, two lowlevel features that in real life can a#ect the underlying network infrastructure and, hence, the ability of processes to perform remote operations.
The pairing of contracts and session types
"... Dedicated to Ugo Montanari in occasion of his 65th birthday Abstract. We pair session types and contracts using two encodings. The encoding of session types accommodates width and depth subtyping, two properties that partially hold in contracts. The encoding of contracts accommodates complex synchro ..."
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Cited by 4 (1 self)
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Dedicated to Ugo Montanari in occasion of his 65th birthday Abstract. We pair session types and contracts using two encodings. The encoding of session types accommodates width and depth subtyping, two properties that partially hold in contracts. The encoding of contracts accommodates complex synchronization patterns, since session types own a simple control protocol. The encodings allow one to use the two formalisms interchangeably, within the context of dyadic interactions. 1
Divergence in Testing and Readiness Semantics
"... Many variants of musttesting equivalence have been put forward that are equally sensitive to deadlock, but differ for the stress they put on divergence, i.e. on the possibility for systems of getting involved in infinite internal computations. Safe testing equivalence is one of such variants, that ..."
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Many variants of musttesting equivalence have been put forward that are equally sensitive to deadlock, but differ for the stress they put on divergence, i.e. on the possibility for systems of getting involved in infinite internal computations. Safe testing equivalence is one of such variants, that naturally pops up when studying the behavioural precongruences induced by certain basic observables. Here, we study the relationships between safe testing and Olderog's readiness semantics, an equivalence induced by a natural process logic. We show that safe testing is finer than readiness equivalence, and coincides with a refinement of this semantics, obtained by a fine tuning of Olderog's definition. For both safe testing and the original readiness semantics we propose simple complete axiomatizations, which permit a fuller appreciation of these equivalences and of their similarities. 1 Introduction Divergence represents the possibility for a system of getting involved in an infinite seq...