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Axiomatisations of Weak Equivalences for De Simone Languages
 Proceedings of the 6th International Conference on Concurrency Theory CONCUR'95
, 1995
"... . Aceto, Bloom and Vaandrager proposed in [ABV92] a procedure for generating a complete axiomatisation of strong bisimulation for process languages in the GSOS format. However, the choice operator +, which the procedure uses, as well as other auxiliary GSOS operators, which it introduces to obtain a ..."
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Cited by 9 (2 self)
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. Aceto, Bloom and Vaandrager proposed in [ABV92] a procedure for generating a complete axiomatisation of strong bisimulation for process languages in the GSOS format. However, the choice operator +, which the procedure uses, as well as other auxiliary GSOS operators, which it introduces to obtain a finite axiomatisation, do not preserve many of weak equivalences. We propose a modification of this procedure, which works for a subclass of process languages in the De Simone format with a special treatment of silent actions. A choice of such a subclass of process languages guarantees that all the considered and auxiliary operators preserve many of weak equivalences. Our procedure generates a complete axiomatisation of refusal simulation preorder and it can be easily adapted to coarser preorders. The completeness result depends on the completeness result for the basic process language, which we prove. This language does not use prefixing with ø and the choice operator +. Instead, we employ...
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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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.
Formats of Ordered SOS Rules with Silent Actions
 Proceedings 7th Conference on Theory and Practice of Software Development (TAPSOFT'97), Lille, LNCS 1214
, 1997
"... We present a general and uniform method for defining structural operational semantics (SOS) of process algebra operators by traditional Plotkinstyle rules equipped with an ordering, the new feature which states the order of application of rules when deriving transitions of process terms. Our method ..."
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Cited by 7 (3 self)
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We present a general and uniform method for defining structural operational semantics (SOS) of process algebra operators by traditional Plotkinstyle rules equipped with an ordering, the new feature which states the order of application of rules when deriving transitions of process terms. Our method allows to represent negative premises and copying in the presence of silent actions. We identify a number of general formats of unordered and ordered rules with silent actions and show that divergence sensitive branching and weak bisimulation relations are preserved by all operators in the relevant formats. A comparison with the existing formats for branching and weak bisimulations shows that our formats are more general.
Ordered SOS Rules and Weak Bisimulation
 Theory and Formal Methods
, 1996
"... this paper we will only consider those formats of rules which treat silent actions as invisible; for example the formats in [8, 10, 11, 9, 12]. A number of important results were established for these formats. Firstly, certain weak equivalences were shown to be preserved by all process operators in ..."
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Cited by 4 (3 self)
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this paper we will only consider those formats of rules which treat silent actions as invisible; for example the formats in [8, 10, 11, 9, 12]. A number of important results were established for these formats. Firstly, certain weak equivalences were shown to be preserved by all process operators in these formats [10, 9, 12]. Secondly, (completed) trace congruences with respect to these formats were discovered [10, 11]. Thirdly, algorithms for generating complete axiomatisations of some weak equivalences were developed [13, 14, 15]. The main conceptual contribution of the paper is a new method for defining process operators, including the sequential composition and priority operators, by transition rules with no negative antecedents. Our method is based on a simple idea of ordering the transition rules for each operator. The behaviour of a process can then be determined by examining the rules of its main operator, starting with the rules highest in the ordering and then considering the rules lower in the ordering. As a result, a rule lower in the ordering can only be applied if none of the rules above it can. Intuitively, this has the effect of applying a rule with negative antecedents. A simple example is given to illustrate our method. Consider a priority operator `, which gives a a priority over b, defined by the following rules.
Ordered SOS Process Languages for Branching and Eager Bisimulations
 INFORMATION AND COMPUTATION
, 2002
"... We present a general and uniform method for defining structural operational semantics (SOS) of process operators by traditional Plotkinstyle transition rules equipped with orderings. This new feature allows one to control the order of application of rules when deriving transitions of process terms. ..."
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Cited by 2 (0 self)
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We present a general and uniform method for defining structural operational semantics (SOS) of process operators by traditional Plotkinstyle transition rules equipped with orderings. This new feature allows one to control the order of application of rules when deriving transitions of process terms. Our method is powerful enough to deal with rules with negative premises and copying. We show that rules with orderings, called ordered SOS rules, have the same expressive power as GSOS rules. We identify several classes of process languages with operators defined by rules with and without orderings in the setting with silent actions and divergence. We prove that branching bisimulation and eager bisimulation relations are preserved by all operators in process languages in the relevant classes.
Stable and Timed Formats for Process Algebra
, 1995
"... We propose a format of transition rules (stable format) for processes which extends De Simone's in that it admits process operators which recognise stability, that is, the inability to perform autonomous actions. The format uses negative premises, but differently from previously proposed format ..."
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Cited by 1 (1 self)
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We propose a format of transition rules (stable format) for processes which extends De Simone's in that it admits process operators which recognise stability, that is, the inability to perform autonomous actions. The format uses negative premises, but differently from previously proposed formats. We show that refusal testing is the trace congruence generated by the format. We identify a subformat (timed format) which serves as a format for discretetimed process algebra in the style of Hennessy and Regan's TPL. 1. Introduction It is wellknown how to use syntaxdirected rules to associate labelled transition systems with terms in process algebra. This is often called structured operational semantics (SOS) [Plo81], and was pioneered by Milner for CCS [Mil80, Mil89]. The meaning of each operator on processes is given by transition rules. We can classify operators according to the form these may take. We say that an operator is in a certain format if its rules belong to that format. Forma...
Abstract
, 2002
"... We observe that equivalence is not a robust concept in the presence of numerical information such as probabilities in the model. We develop a metric analogue of weak bisimulation in the spirit of our earlier work on metric analogues for strong bisimulation. We give a fixed point characterization o ..."
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We observe that equivalence is not a robust concept in the presence of numerical information such as probabilities in the model. We develop a metric analogue of weak bisimulation in the spirit of our earlier work on metric analogues for strong bisimulation. We give a fixed point characterization of the metric. This makes available coinductive reasoning principles and allows us to prove metric analogues of the usual algebraic laws for process combinators. We also show that quantitative properties of interest are continuous with respect to the metric, which says that if two processes are close in the metric then observable quantitative properties of interest are indeed close. As an important example of this we show that nearby processes have nearby channel capacities a quantitative measure of their propensity to leak information. ∗ Research supported by NSERC. † Research supported by NSF. ‡ Research supported in part by NSERC and MITACS. 1
Termination and Confluence of Term Rewrite Systems for GSOS Process Languages
"... We consider the procedures for automatic derivation of axiom systems and term rewrite systems for process language in the GSOS format. We show that, for a decidable subclass of GSOS process languages, namely syntactically wellfounded and linear GSOS process languages, the generated term rewrite sys ..."
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We consider the procedures for automatic derivation of axiom systems and term rewrite systems for process language in the GSOS format. We show that, for a decidable subclass of GSOS process languages, namely syntactically wellfounded and linear GSOS process languages, the generated term rewrite systems are strongly normalising, confluent, and sound and complete for bisimulation modulo the associativity and commutativity of the choice operator on closed terms.