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Automatic Verification of RealTime Communicating Systems by ConstraintSolving
 In Proc. of the 7th International Conference on Formal Description Techniques
, 1994
"... this paper, an algebra of timed processes with realvalued clocks is presented, which serves as a formal description language for realtime communicating systems. We show that requirements such as "a process will never reach an undesired state" can be verified by solving a simple class o ..."
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Cited by 45 (15 self)
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this paper, an algebra of timed processes with realvalued clocks is presented, which serves as a formal description language for realtime communicating systems. We show that requirements such as "a process will never reach an undesired state" can be verified by solving a simple class of constraint systems on the clockvariables. A complete method for reachability analysis associated with the language is developed, and implemented as an automatic verification tool based on constraintsolving techniques. Finally as examples, we study and verify the safetyproperties of Fischer's mutual exclusion protocol and a railway crossing controller.
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.
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...
On Modeling Realtime Mobile Processes
 IN PROCEEDINGS OF THE TWENTYFIFTH AUSTRALASIAN CONFERENCE ON COMPUTER SCIENCE (2002
, 2002
"... This paper introduces an algebra for modeling the realtime aspect of systems in a mobile environment. Our model makes use of many familiar concepts and properties from previous works on static, realtime process algebra, and incorporates these into Milner's dynamic picalculus. The extended al ..."
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This paper introduces an algebra for modeling the realtime aspect of systems in a mobile environment. Our model makes use of many familiar concepts and properties from previous works on static, realtime process algebra, and incorporates these into Milner's dynamic picalculus. The extended algebra allows both time values as well as names to be transmitted between processes, thereby allowing the modeling of, and reasoning about, dynamic temporal behaviour and dynamic configurations of systems. Further, conventional labeled transition system (LTS) semantics are found to be inadequately expres sive for use with our algebra. We therefore propose a timed labeled transition system (TLTS) semantics. Finally, we illustrate the modeling power of our algebra with a comprehensive but simple example of a mobile streaming video player.
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 3 (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.
Local Model Checking for RealTime Systems (Extended Abstract)
 In Proceedings of the 7th International Conference on ComputerAided Verification. American Mathematical Society
, 1995
"... ) ? Oleg V. Sokolsky Scott A. Smolka Department of Computer Science SUNY at Stony Brook Stony Brook, NY 117944400 foleg,sasg@cs.sunysb.edu Abstract. We present a local algorithm for model checking in a realtime extension of the modal mucalculus. As such, the whole state space of the realtime s ..."
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) ? Oleg V. Sokolsky Scott A. Smolka Department of Computer Science SUNY at Stony Brook Stony Brook, NY 117944400 foleg,sasg@cs.sunysb.edu Abstract. We present a local algorithm for model checking in a realtime extension of the modal mucalculus. As such, the whole state space of the realtime system under investigation need not be explored, but rather only that portion necessary to determine the truthhood of the logical formula. To the best of our knowledge, this is the first local algorithm for the verification of realtime systems to appear in the literature. Like most algorithms dealing with realtime systems, we work with a finite quotient of the inherently infinite state space. For maximal efficiency, we obtain, onthefly, a quotient that is as coarse as possible in the following sense: refinements of the quotient are carried out only when necessary to satisfy clock constraints appearing in the logical formula or timed automaton used to represent the system under investigati...
Verifying a Video Signal Delay Buffer in a Timed Process Calculus
, 1994
"... We present a simple real time system and its modelling in a timed process calculus. The problem concerns a delay buffer for video signals, a device which for example is needed to delay television broadcasts of sport events in situations when the delay time is less than the total broadcast duration. ..."
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We present a simple real time system and its modelling in a timed process calculus. The problem concerns a delay buffer for video signals, a device which for example is needed to delay television broadcasts of sport events in situations when the delay time is less than the total broadcast duration. Since digitised video information requires vast amount of memory, it is still not realistic to use traditional digital disc media to implement buffers for the typical delay times that are common. The usual approach is instead to use three or more computer controlled video machines which cooperate to solve the task. We describe the specification and implementation of such a system at a rather high level of abstraction in a timed version of CCS. The implementation is decomposed into two levels of abstraction, thereby separating high level timing constraint issues from the low level controlling of the machines. Moreover we prove that the implementation is correct up to weak timed bisimulation e...
Decidability of Timed LanguageInclusion for Networks of RealTime Communicating Sequential Processes
, 1994
"... . An important verification problem for concurrent systems in general is that of establishing whether one system is a correct implementation, or refinement, of another system. For untimed systems, trace inclusion (or variants such as failure inclusion) is often used as a criterion of refinement. The ..."
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. An important verification problem for concurrent systems in general is that of establishing whether one system is a correct implementation, or refinement, of another system. For untimed systems, trace inclusion (or variants such as failure inclusion) is often used as a criterion of refinement. The natural extension of this criterion to timed systems is timed traceinclusion. Unfortunately, this problem is undecidable for the commonly used model of timed automata (i.e. finitestate automata extended with clocks) due to the expressive power of the model. This is a serious obstacle to the application of automatic verification methods to timed automata. In this paper, we show that the problem of timed traceinclusion is decidable for a large and natural class of processes in Reed and Roscoe's Timed CSP [RR86]. Essentially, this class includes static networks of processes with finitecontrol structure and realvalued clocks (modelled implicitly by a delay operator). 1 Introduction Tr...
On Broadcast and Real Time in Process Calculi
, 1994
"... In this thesis we investigate several questions in the field of process calculi related to Milner's CCS. We show relationships between broadcasting and the notion of pure synchrony; we investigate and apply a realtime version of CCS; and we discuss sort computation and translation of static pr ..."
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In this thesis we investigate several questions in the field of process calculi related to Milner's CCS. We show relationships between broadcasting and the notion of pure synchrony; we investigate and apply a realtime version of CCS; and we discuss sort computation and translation of static process expressions. The thesis consists of the following five selfcontained parts, where the main contributions are found in the two first. In the broadcast calculus CBS, the traditional symmetric handshake synchronisation paradigm of most process calculi, has been replaced by nonsymmetric unbuffered broadcast. Senders are active and autonomous, receivers are passive and controlled. The sending and reception of a broadcast is a synchronous atomic action. In the first part we give a translation from CBS into Milner's synchronous calculus SCCS, which demonstrates that broadcasting can be encoded in SCCS, and that CBS is not primitive. The second part presents decidability results for a regular su...