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Branching Time and Abstraction in Bisimulation Semantics
 Journal of the ACM
, 1996
"... Abstract. In comparative concurrency semantics, one usually distinguishes between linear time and branching time semantic equivalences. Milner’s notion of ohsen~ation equirlalence is often mentioned as the standard example of a branching time equivalence. In this paper we investigate whether observa ..."
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Cited by 322 (17 self)
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Abstract. In comparative concurrency semantics, one usually distinguishes between linear time and branching time semantic equivalences. Milner’s notion of ohsen~ation equirlalence is often mentioned as the standard example of a branching time equivalence. In this paper we investigate whether observation equivalence really does respect the branching structure of processes, and find that in the presence of the unobservable action 7 of CCS this is not the case. Therefore, the notion of branching hisimulation equivalence is introduced which strongly preserves the branching structure of processes, in the sense that it preserves computations together with the potentials in all intermediate states that are passed through, even if silent moves are involved. On closed KSterms branching bisimulation congruence can be completely axiomatized by the single axiom scheme: a.(7.(y + z) + y) = a.(y + z) (where a ranges over all actions) and the usual laws for strong congruence. WC also establish that for sequential processes observation equivalence is not preserved under refinement of actions, whereas branching bisimulation is. For a large class of processes, it turns out that branching bisimulation and observation equivalence are the same. As far as we know, all protocols that have been verified in the setting of observation equivalence happen to fit in this class, and hence are also valid in the stronger setting of branching hisimulation equivalence.
Termination in Timed Process Algebra
 Formal Aspects of Computing
, 2000
"... We investigate different forms of termination in timed process algebras. The integrated framework of discrete and dense time, relative and absolute time process algebras is extended with forms of successful and unsuccessful termination. The different algebras are interrelated by embeddings and conse ..."
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Cited by 170 (25 self)
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We investigate different forms of termination in timed process algebras. The integrated framework of discrete and dense time, relative and absolute time process algebras is extended with forms of successful and unsuccessful termination. The different algebras are interrelated by embeddings and conservative extensions.
Process Theory Based on Bisimulation Semantics
 In Linear Time, Branching Time and Partial Order in Logics and Models for Concurrency, LNCS 354
, 1988
"... Permission of the editors to include the present Chapter I here is gratefully acknowledged. In this paper a process is viewed as a labeled graph modulo bisimulation equivalence. Three topics are covered: (i) specification of pr cesses using finite systems of quations over the syntax of process algeb ..."
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Cited by 34 (1 self)
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Permission of the editors to include the present Chapter I here is gratefully acknowledged. In this paper a process is viewed as a labeled graph modulo bisimulation equivalence. Three topics are covered: (i) specification of pr cesses using finite systems of quations over the syntax of process algebra; (ii) inference systems which are complete for proving the equivalence of regular (finite state) processes; (iii) variations of the bisimulation model. I n t roduct ion We will discuss process theory on the basis of a given semantic oncept. A process will be a rooted directed graph where arcs are labeled with actions. An example may clarify this matter (see Figure
A Complete Axiomatization for Branching Bisimulation Congruence of FiniteState Behaviours
 In Proc. MFCS’93, LNCS 711
, 1993
"... ion is usually performed by turning actions that are considered unimportant into the invisible action ø . Then, a system that after some activity reaches a state from which only an invisible action is possible, leading to another state, is considered equivalent to an otherwise identical system, that ..."
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Cited by 32 (2 self)
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ion is usually performed by turning actions that are considered unimportant into the invisible action ø . Then, a system that after some activity reaches a state from which only an invisible action is possible, leading to another state, is considered equivalent to an otherwise identical system, that after said activity immediately reaches the other state. Thus the mechanism of abstraction by hiding of irrelevant or unobservable actions needs support from the congruence notion employed. There are many ways to extend bisimulation congruence to processes with hidden moves. The simplest generalization is strong (bisimulation) equivalence, in which øactions are treated no different than visible actions. For this reason strong congruence is not abstract in the sense stipulated above. Another option is to take the testing scenario underlying bisimulation equivalence as primary, incorporating the unobservable nature of hidden moves. This yields Milner's notion of weak (bisimulation) congruenc...
Modal Logic, Transition Systems and Processes
, 1994
"... Transition systems can be viewed either as process diagrams or as Kripke structures. The first perspective is that of process theory, the second that of modal logic. This paper shows how various formalisms of modal logic can be brought to bear on processes. Notions of bisimulation can not only be mo ..."
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Cited by 23 (3 self)
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Transition systems can be viewed either as process diagrams or as Kripke structures. The first perspective is that of process theory, the second that of modal logic. This paper shows how various formalisms of modal logic can be brought to bear on processes. Notions of bisimulation can not only be motivated by operations on transition systems, but they can also be suggested by investigations of modal formalisms. To show that the equational view of processes from process algebra is closely related to modal logic, we consider various ways of looking at the relation between the calculus of basic process algebra and propositional dynamic logic. More concretely, the paper contains preservation results for various bisimulation notions, a result on the expressive power of propositional dynamic logic, and a definition of bisimulation which is the proper notion of invariance for concurrent propositional dynamic logic. Keywords: modal logic, transition systems, bisimulation, process algebra 1 In...
Compositional reasoning for probabilistic finitestate behaviors
 In Processes, Terms and Cycles: Steps on the Road to Infinity, Essays Dedicated to Jan Willem Klop, on the Occasion of His 60th Birthday, LNCS 3838
, 2005
"... Abstract. We study a process algebra which combines both nondeterministic and probabilistic behavior in the style of Segala and Lynch’s simple probabilistic automata. We consider strong bisimulation and observational equivalence, and provide complete axiomatizations for a language that includes para ..."
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Cited by 15 (6 self)
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Abstract. We study a process algebra which combines both nondeterministic and probabilistic behavior in the style of Segala and Lynch’s simple probabilistic automata. We consider strong bisimulation and observational equivalence, and provide complete axiomatizations for a language that includes parallel composition and (guarded) recursion. The presence of the parallel composition introduces various technical difficulties and some restrictions are necessary in order to achieve complete axiomatizations. 1
Finite axiom systems for testing preorder and De Simone Process Languages
, 2000
"... We prove that testing preorder of De Nicola and Hennessy is preserved by all operators of De Simone process languages. Building upon this result we propose an algorithm for generating axiomatisations of testing preorder for arbitrary De Simone process languages. The axiom systems produced by our alg ..."
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Cited by 10 (2 self)
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We prove that testing preorder of De Nicola and Hennessy is preserved by all operators of De Simone process languages. Building upon this result we propose an algorithm for generating axiomatisations of testing preorder for arbitrary De Simone process languages. The axiom systems produced by our algorithm are finite and complete for processes with nite behaviour. In order to achieve completeness for a subclass of processes with infiite behaviour we use one infinitary induction rule. The usefulness of our results is illustrated in specification and verification of small concurrent systems, where suspension, resumption and alternation of execution of component systems occur. We argue that better speci cations can be written in customised De Simone process languages, which contain both the standard operators as well as new De Simone operators that are specifically tailored for the task in hand. Moreover, the automatically generated axiom systems for such specification languages make the verification more straightforward.
A Paradigm for Asynchronous Communication and its Application to Concurrent Constraint Programming
 Logic programming languages: constraints, functions, and objects, Logic Programming Series
, 1993
"... We develop a general semantic theory of asynchronous communication in concurrent logic and concurrent constraint languages. The main characteristic of these languages, from the point of view of the communication mechanism, is that processes interact by querying and updating some common data structur ..."
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Cited by 6 (3 self)
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We develop a general semantic theory of asynchronous communication in concurrent logic and concurrent constraint languages. The main characteristic of these languages, from the point of view of the communication mechanism, is that processes interact by querying and updating some common data structure. We abstract from the specific features of the underlying data structure by means of a uniform language of which the actions are interpreted as transformations on an abstract set of states. This approach shows that there exists a basic similarity between concurrent logic (constraint) languages and other languages based on asynchrononous communication, like dataflow and asynchronous CSP. Actually, our intention is to capture languages based on asynchronous communication as instances of this uniform language, such an instance being determined by a specific set of states and interpretation of the actions. The computational model of our paradigm is described by a transition system in the style...
An Axiomatization for Regular Processes in Timed Branching Bisimulation
 Fundamenta Informaticae
, 1998
"... ion The previous section treated BPA ffir with recursion modulo timed strong bisimulation. In this section the alphabet is extended with a special constant ø , to obtain BPA ffiø r with recursion, and process terms are considered modulo rooted timed branching bisimulation. In the sequel, a and ff w ..."
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Cited by 5 (0 self)
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ion The previous section treated BPA ffir with recursion modulo timed strong bisimulation. In this section the alphabet is extended with a special constant ø , to obtain BPA ffiø r with recursion, and process terms are considered modulo rooted timed branching bisimulation. In the sequel, a and ff will represent elements from A [ føg and A [ fffi; øg, respectively. 3.1 Time Shift In order to define timed branching bisimulation, the syntax is extended with the time shift operator (r)p, which takes a rational number r and a process term p. The process term (r)p denotes the behaviour of p that is shifted r units in time. Its ultimate delay is defined by U((r)p) = maxfU(p) + r; 0g The transition rules and axioms for the time shift are given in Table 4. Using axioms TS14, this operator can be eliminated from all process terms. 3.2 Timed Branching Bisimulation The operational semantics consists of the transition rules in Table 1 and Table 2 and Table 4. The definition of timed strong...
Unique Fixpoint Induction for MessagePassing Process Calculi
 Australia Computer Science Communications
, 1997
"... We present a proof system for messagepassing process calculi with recursion. The key inference rule to deal with recursive processes is a version of Unique Fixpoint Induction for process abstractions. We prove the proof system is sound and also complete for a restricted form of regular messagepassi ..."
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Cited by 5 (1 self)
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We present a proof system for messagepassing process calculi with recursion. The key inference rule to deal with recursive processes is a version of Unique Fixpoint Induction for process abstractions. We prove the proof system is sound and also complete for a restricted form of regular messagepassing processes. We also show that the system is incomplete in general and discuss more powerful extensions with inductive inference rules.