## Basic Observables for Processes (1999)

Venue: | Information and Computation |

Citations: | 14 - 5 self |

### BibTeX

@ARTICLE{Boreale99basicobservables,

author = {Michele Boreale and Rocco De Nicola and Rosario Pugliese},

title = {Basic Observables for Processes},

journal = {Information and Computation},

year = {1999},

volume = {149},

pages = {95--109}

}

### Years of Citing Articles

### OpenURL

### Abstract

A general approach for defining behavioural preorders over process terms as the maximal pre--congruences 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 pre--congruences 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 safe--must, 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...

### Citations

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Citation Context ... such as fair testing. In [28], two Petri nets are called d--equivalent if they both can reach a deadlocked state or if they both cannot do so. Then it is proved that the variant of failure semantics =-=[6]-=- that ignores divergence is obtained by closing d--equivalence with respect to parallel composition. In [14], a series of variants of the testing framework are proposed and results are listed that sho... |

3281 |
Communication and Concurrency
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Citation Context ...s out to be much less obvious. A first attempt at approaching the problem of process equivalences along the mentioned lines is described in [19]. Milner and Sangiorgi define a new equivalence for CCS =-=[18]-=- based on barbed bisimilarity. This relation represents a uniform basis for defining sensible process equivalences for different languages, as it only relies on a reduction relation and an observation... |

415 | Testing equivalences for processes
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Citation Context ...n isolation we will also study the result of using them in pairs and shall show that: ffl # �� c L , the contextual preorder induced by # and ! `, coincides with ! ��M , the original must preo=-=rder of [9, 13]; ffl #L-=- �� c L , the contextual preorder induced by # ` and ! `, gives rise to a new preorder, the safe--must preorder ! �� SM , which is also supported by a very intuitive testing scenario. Table 1 ... |

400 |
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Citation Context ...n isolation we will also study the result of using them in pairs and shall show that: ffl # �� c L , the contextual preorder induced by # and ! `, coincides with ! ��M , the original must preo=-=rder of [9, 13]; ffl #L-=- �� c L , the contextual preorder induced by # ` and ! `, gives rise to a new preorder, the safe--must preorder ! �� SM , which is also supported by a very intuitive testing scenario. Table 1 ... |

269 | A calculus of mobile agents
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Citation Context ...--congruence of [9]; here we have proved this conjecture. Laneve discusses the impact of an observables-based testing scenario on the Join Calculus, a language with elaborate synchronization schemata =-=[12]-=-. Acknowledgments We are grateful to L. Aceto, F. van Breugel, W. Ferreira, E.-R. Olderog, A. Rensink and W. Vogler for interesting discussions and suggestions and to F. Focardi for a first debugging ... |

239 | The lazy lambda calculus
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Citation Context ... CNR project "Specifica ad alto livello e verifica formale di sistemi digitali" and by Istituto di Elaborazione dell'Informazione CNR, Pisa. A similar approach, used e.g. for the lazy lambda=-= calculus [1]-=-, is that of defining equivalence relations in terms of reduction to normal forms. It leads to considering as equivalent any two programs that cannot be differentiated by considering the possibility o... |

226 | Barbed bisimulation
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Citation Context ...of concurrent components via their contextual behaviour turns out to be much less obvious. A first attempt at approaching the problem of process equivalences along the mentioned lines is described in =-=[19]-=-. Milner and Sangiorgi define a new equivalence for CCS [18] based on barbed bisimilarity. This relation represents a uniform basis for defining sensible process equivalences for different languages, ... |

156 |
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Citation Context ...hich decreases whenever an internal action takes place. ffl Distribution of systems can be observed by tagging visible actions with some information about the location where they take place, see e.g. =-=[7, 3]-=-. A natural choice for us would be to consider a guarantee predicate of the form P !(`@u), where u is a locality in the sense of [3]. If the language is extended with a parallel composition operator w... |

142 | An overview and synthesis on timed process algebras
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Citation Context ...tagged with the same locality, it should not be difficult to establish full abstraction results for the resulting testing theories. ffl Timing aspects of processes behaviour are elegantly modelled in =-=[29, 30, 23] by adopti-=-ng a two-phase operational semantics. One phase models occurrence of usual atomic actions, the other models time passing via "idling" transitions, of the form P d \Gamma! P 0 (d non-negative... |

130 |
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Citation Context ...ging terms in any context. In general, given a language equipped with a reduction relation, the paradigm for defining preorders (equivalences) over terms of the language, can be traced back to Morris =-=[20]-=- and can be phrased as follows: 1. Define a set of observables (values, normal forms, . . . ) to which a program can evaluate by means of successive reductions. 2. Define a basic preorder over terms b... |

93 |
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Citation Context ...ng communications along specific channels is not sufficient. Indeed, considering just the possibility of communication and closing with respect to all contexts would lead to trace semantics (see e.g. =-=[8]-=-), that totally ignores possible deadlocks and other liveness properties. Due to the inherent nondeterminism of concurrent computations, to get more inspective semantics it is necessary to know whethe... |

84 |
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(Show Context)
Citation Context ...n operator for internal choice and an operator for purely external choice 1 . 1 These choice operators were originally introduced by Hoare, see e.g. [15], their operational semantics was described in =-=[25]. communication requirements-=- 8 ! : convergence requirements z --- -- no req. convergence: # conv. after `: # ` no req. U # �� c , ! �� CT #L �� c , ! �� CT guarantee `: ! ` �� c L , ! �� c FS # �� c L... |

72 | An EÆciency Preorder for Processes
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(Show Context)
Citation Context ...idering a richer base language than TCCS. Below, we discuss a few possible generalizations. ffl Efficiency can be taken into consideration by counting the number of internal actions, in the spirit of =-=[2, 22]. To-=- capture the above within our setting, we can refine the guarantee predicate with information about the number of ��! -- reductions needed to reach a state capable of the visible action. More prec... |

60 | Fair testing
- Rensink, Vogler
- 2007
(Show Context)
Citation Context ...ure. More specifically, we will show that: ffl �� c L , the contextual preorder induced by ! `, coincides with ! �� c FS , the maximal pre--congruence included in the fair/should preorder of [=-=21] and [4]. ffl # ��-=-�� c and #L �� c , the contextual preorders induced by # and # `, both coincide with ! �� CT , the preorder given by reverse inclusion of convergent traces. This is the maximal refinement of t... |

43 |
Observing localities
- Boudol, Castellani, et al.
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(Show Context)
Citation Context ...hich decreases whenever an internal action takes place. ffl Distribution of systems can be observed by tagging visible actions with some information about the location where they take place, see e.g. =-=[7, 3]-=-. A natural choice for us would be to consider a guarantee predicate of the form P !(`@u), where u is a locality in the sense of [3]. If the language is extended with a parallel composition operator w... |

42 |
Real-time behaviour of asynchronous agents. CONCUR ’90 Theories of Concurrency: Unification and Extension
- Wang
- 1990
(Show Context)
Citation Context ...tagged with the same locality, it should not be difficult to establish full abstraction results for the resulting testing theories. ffl Timing aspects of processes behaviour are elegantly modelled in =-=[29, 30, 23] by adopti-=-ng a two-phase operational semantics. One phase models occurrence of usual atomic actions, the other models time passing via "idling" transitions, of the form P d \Gamma! P 0 (d non-negative... |

41 | Divergence and fair testing
- Natarajan, Cleaveland
- 1995
(Show Context)
Citation Context ...e literature. More specifically, we will show that: ffl �� c L , the contextual preorder induced by ! `, coincides with ! �� c FS , the maximal pre--congruence included in the fair/should preo=-=rder of [21] and [4]. ff-=-l # �� c and #L �� c , the contextual preorders induced by # and # `, both coincide with ! �� CT , the preorder given by reverse inclusion of convergent traces. This is the maximal refinem... |

34 | Concurrent ML : Design, application and semantics
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(Show Context)
Citation Context ...ra uses a predicate which resembles very much the conjunction of our # and ! ` (based on production of values rather than on communication capabilities) to define a testing preorder for Concurrent ML =-=[27]-=-; this seems to be strongly related to our safe--must preorder. He also conjectures that if one considers pure CCS (and observes communication capabilities instead of value productions) the obtained p... |

32 |
Nets, terms, and formulas
- Olderog
- 1991
(Show Context)
Citation Context ...this explains the adjective `safe'). This condition is stronger than the one introduced by De Nicola and Hennessy [9] and is very closely related to the definition of Olderog's readiness semantics in =-=[24]-=-. The rest of the paper is organized as follows. In Section 2, we briefly recall syntax and transitional semantics of TCCS. In Section 3, we introduce the relevant notions of the observational semanti... |

23 | Correspondence between operational and denotational semantics: the full abstraction problem for PCF” in handbook of logic in computer science
- Ong
- 1995
(Show Context)
Citation Context ...ce over the language induced by the basic preorder. This paradigm has been the basis for assessing many semantics of sequential languages and is at the heart of the full abstraction problem, see e.g. =-=[26]-=-. Here, we aim at taking advantage of this paradigm also for studying models of concurrent systems and their equivalences. In this case, the choice of the basic observables is less obvious. It is well... |

23 |
CCS + Time = an Interleaving Model for Real Time Systems
- Wang
- 1991
(Show Context)
Citation Context ...tagged with the same locality, it should not be difficult to establish full abstraction results for the resulting testing theories. ffl Timing aspects of processes behaviour are elegantly modelled in =-=[29, 30, 23] by adopti-=-ng a two-phase operational semantics. One phase models occurrence of usual atomic actions, the other models time passing via "idling" transitions, of the form P d \Gamma! P 0 (d non-negative... |

19 | ccs without ⌧’s - Nicola, Hennessy - 1987 |

13 |
failure and testing equivalences for communicating processes
- Trace
- 1987
(Show Context)
Citation Context ... but C a;fbg 5 [a:b:\Omega\Gamma "). This would invalidate the proof of the "if" part of Theorem 4.11. Indeed, the use of a context very similar to our C s;B 5 invalidates a proof in a =-=paper by Main ([17]-=-, Lemma 4.2), where the relationships between the must and the maximal trace preorders are studied. 5 An Assessment of the Preorders In this section we explore the relationships among the preorders we... |

12 | An Algebraic Theory of Process Efficiency
- Natarajan, Cleaveland
- 1996
(Show Context)
Citation Context ...idering a richer base language than TCCS. Below, we discuss a few possible generalizations. ffl Efficiency can be taken into consideration by counting the number of internal actions, in the spirit of =-=[2, 22]. To-=- capture the above within our setting, we can refine the guarantee predicate with information about the number of ��! -- reductions needed to reach a state capable of the visible action. More prec... |

10 | and Must Testing in the Join-Calculus
- Laneve
(Show Context)
Citation Context ...enable to automatic checking. Beside Milner and Sangiorgi [19], notions of observables in the same spirit as ours have been proposed by Main [17], Vogler [28], Hennessy [14], Ferreira [11] and Laneve =-=[16]-=-. In [17], it is shown that the pre--congruence induced by the preorder based on inclusion of maximal traces coincides, both for CCS and CSP, with the must pre-- congruence of [9]; another characteriz... |

6 |
Failures semantics and deadlocking of modular petri nets
- Vogler
- 1988
(Show Context)
Citation Context ...to assess alternative characterization more amenable to automatic checking. Beside Milner and Sangiorgi [19], notions of observables in the same spirit as ours have been proposed by Main [17], Vogler =-=[28]-=-, Hennessy [14], Ferreira [11] and Laneve [16]. In [17], it is shown that the pre--congruence induced by the preorder based on inclusion of maximal traces coincides, both for CCS and CSP, with the mus... |

2 |
Semantic theories for concurrent ML
- Ferreira
- 1995
(Show Context)
Citation Context ...rization more amenable to automatic checking. Beside Milner and Sangiorgi [19], notions of observables in the same spirit as ours have been proposed by Main [17], Vogler [28], Hennessy [14], Ferreira =-=[11]-=- and Laneve [16]. In [17], it is shown that the pre--congruence induced by the preorder based on inclusion of maximal traces coincides, both for CCS and CSP, with the must pre-- congruence of [9]; ano... |

1 |
Observing Processes. In Linear Time, Branching Time and Partial Order in Logics and Models for Concurrency
- Hennessy
- 1989
(Show Context)
Citation Context ...native characterization more amenable to automatic checking. Beside Milner and Sangiorgi [19], notions of observables in the same spirit as ours have been proposed by Main [17], Vogler [28], Hennessy =-=[14]-=-, Ferreira [11] and Laneve [16]. In [17], it is shown that the pre--congruence induced by the preorder based on inclusion of maximal traces coincides, both for CCS and CSP, with the must pre-- congrue... |