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Weak Sequential Composition in Process Algebras
 CONCUR'94: Concurrency Theory, volume 836 of Lecture Notes in Computer Science
, 1994
"... . In this paper we study a special operator for sequential composition, which is defined relative to a dependency relation over the actions of a given system. The idea is that actions which are not dependent (intuitively because they share no common resources) do not have to wait for one another to ..."
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. In this paper we study a special operator for sequential composition, which is defined relative to a dependency relation over the actions of a given system. The idea is that actions which are not dependent (intuitively because they share no common resources) do not have to wait for one another to proceed, even if they are composed sequentially. Such a notion has been studied before in a lineartime setting, but until recently there has been no systematic investigation in the context of process algebras. We give a structural operational semantics for a process algebraic language containing such a sequential composition operator, which shows some interesting interplay with choice. We give a complete axiomatisation of strong bisimilarity and we show consistency of the operational semantics with an eventbased denotational semantics developed recently by the second author. The axiom system allows to derive the communication closed layers law, which in the linear time setting has been sho...
Metric Semantics and Full Abstractness for Action Refinement and Probabilistic Choice
, 2001
"... This paper provides a casestudy in the eld of metric semantics for probabilistic programming. Both an operational and a denotational semantics are presented for an abstract process language L pr , which features action refinement and probabilistic choice. The two models are constructed in the setti ..."
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This paper provides a casestudy in the eld of metric semantics for probabilistic programming. Both an operational and a denotational semantics are presented for an abstract process language L pr , which features action refinement and probabilistic choice. The two models are constructed in the setting of complete ultrametric spaces, here based on probability measures of compact support over sequences of actions. It is shown that the standard toolkit for metric semantics works well in the probabilistic context of L pr , e.g. in establishing the correctness of the denotational semantics with respect to the operational one. In addition, it is shown how the method of proving full abstraction  as proposed recently by the authors for a nondeterministic language with action refinement  can be adapted to deal with the probabilistic language L pr as well.
SVV Preliminary Version Compositional Properties of Sequential Processes
"... It is widely agreed that the modular method is one of the most eective methods to specify and verify complex systems in order to avoid combinatorial explosion. FLC ( Fixpoint Logic with Chop) is an important modal logic because of its expressivity and logic properties, e.g., it is strictly more expr ..."
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It is widely agreed that the modular method is one of the most eective methods to specify and verify complex systems in order to avoid combinatorial explosion. FLC ( Fixpoint Logic with Chop) is an important modal logic because of its expressivity and logic properties, e.g., it is strictly more expressive than the calculus. In this paper, we study the compositionality of FLC, namely, to investigate the connection between the connectives of the logic and the constructors of programs. To this end, we rst extend FLC with a nondeterministic operator \+ " (FLC+ for the extension) and then establish a correspondence between the logic and the basic process algebra with deadlock and termination (abbreviated by BPA). Finally, we show that as a byproduct of the correspondence characteristic formulae for processes of BPA up to strong (observational) bisimulation can be constructed compositionally directly from the syntax of processes. Key words: chop operator, modal logic, compositionality, veri cation, bisimulation, characteristic formula, process algebra 1
Vertical Bisimulation
, 1998
"... We investigate criteria to relate specifications and implementations belonging to conceptually dfferent abstraction levels, and we propose vertical bisimulation as a candidate relation for this purpose. Vertical bisimulation is indexed by a function mapping abstract actions onto concrete processes, ..."
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We investigate criteria to relate specifications and implementations belonging to conceptually dfferent abstraction levels, and we propose vertical bisimulation as a candidate relation for this purpose. Vertical bisimulation is indexed by a function mapping abstract actions onto concrete processes, which lays down the basic connection between the levels. Vertical bisimulation is compatible with the standard interleaving semantics; in fact, if the refinement function is the identity, then vertical bisimulation collapses to the standard notion of rooted bisimulation. We prove that vertical bisimulation satisfies a number of congruencelike proof rules (notably a structural one for recursion) that offer a powerful, compositional proof technique to verify whether a certain process is an implementation for some speci cation. We give a number of small examples to demonstrate the advantages of this approach.
in: MFCS'97, Peter Ruzicka (Ed.) Dependencybased action renement
"... Abstract. Action renement in process algebras has been widely studied in the last few years as a means to support topdown design of systems. A specic notion of renement arises when a dependency relation on the actions (in the Mazurkiewicz sense) is used to control the inheritance of orderings fr ..."
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Abstract. Action renement in process algebras has been widely studied in the last few years as a means to support topdown design of systems. A specic notion of renement arises when a dependency relation on the actions (in the Mazurkiewicz sense) is used to control the inheritance of orderings from the abstract level. In this paper we present a rather simple operational semantics for dependencybased action renement. We show the consistency of the operational with a (previously published) denotational semantics. We moreover show that bisimulation is a congruence for dependencybased renement. Finally, we give an illustrative example. 1