Wang Yi. Real-time behaviour of asynchronous agents. In Concurrency Theory, volume 458 of Lect. Notes in Comp. Sci., pages 502-520. Springer, 1990. 15  Home/Search   Document Not in Database   Summary   Related Articles   Check

....constructions for timed automata using the logic L # that, like those in the untimed setting and unlike that o#ered in [19] yield formulae whose size is linear with respect to that of the timed automaton they characterize. We present characteristic formula constructions for timed bisimilarity [28], timed versions of the simulation [21] and ready simulation [5, 20] preorders and for the faster than preorder [23] In particular, the characteristic formula construction for timed bisimilarity improves upon that o#ered in [19] In addition, since, if B is a deterministic timed automaton, ....

....) s ## , for some s # # S; 4 . 0 Delay) for every s, s # # S, #(0) s # i# s = s # . As usual, we write s to mean that there is some state s # such that s s # . The axioms of time determinism, time additivity and 0 delay are standard in the literature on Yi s TCCS (see, e.g. [28]) Timed Automata Let C be a set of clocks. We use to denote the set of boolean expressions over atomic formulae of the form x # p and x y # p, with x, y C, p N, and ## , Expressions in are interpreted over the collection of time assignments. A time assignment, or ....

[Article contains additional citation context not shown here]

Y. Wang, Real-time behaviour of asynchronous agents, in Baeten and Klop [4], pp. 502--520. 23 Recent BRICS Report Series Publications RS-00-23 Luca Aceto, Anna Ing olfsd ottir, Mikkel Lykke Pedersen, and Jan Poulsen. Characteristic Formulae for Timed Automata. September 2000.

....this problem in this paper. In the untimed setting, bisimulation equivalences have been reasonably successful as notions of implementation between transition systems [BW90, Mil89] Consequently, bisimulation equivalences have also been proposed as implementation relations for the timed setting [BB91, Klu93, MT90, NS94, Yi90]. However, we do not believe that bisimulations will turn out to be very useful as implementation relations in the timed case. The problem is that they do not allow one to abstract in specifications from the often very complex timing behaviour of implementations (see Chapter 10 of [Klu93] for an ....

....that can block the passage of time, and a RATE operation that can change the speed of its argument. On the other hand, there are several operators that have been proposed in the literature that do not fit our format of action transducers, in particular, the CCS style choice operation present in [BB91, MT90, NS94, Yi90]. This operation cannot be expressed as a timed action transducer because the timed trace inclusion relation is not substitutive with respect to it. We briefly consider the design of an appropriate language of operators for describing timing based systems. Such a language should consist of a ....

[Article contains additional citation context not shown here]

Wang Yi. Real-time behaviour of asynchronous agents. In Baeten and Klop

....with observing a succession of distinct, observable events [L 8] By treating time passing as an explicit event, we can let time pass without any other actions oc curing. See also the time visibility property in sub section 3.3. We use the symbol e(t) to represent this time event as in [W90, W91a] and t represents the number of clock ticks passed in this time event. Separation of actions and time events: As in almost all previous works on real time process algebra, we adopt an interleaving model where we sepa rate time events from normal actions. Synchronous time events: Time ....

....at which they are enabled, and the occurrence (and time) at which they are fired, no matter what timing granularity we may impose. Figure 2 shows two time diagrams that illustrate the two types of actions. 3. 3 Model Properties Many of the following properties are also defined sim ilarly in [W90, W91a, NS91] Enabling and firing of action 2 time Enabling of complementary action Enabling of action by environment x time Firing of action Figure 2: Non controllable action (above) and controllable action (below) Maximal progress: This property states that there is no unnecessary ....

[Article contains additional citation context not shown here]

Y. Wang, "Real-Time Behaviour of Asyn- chronous Agents", Proceedings of CONCUR'90, LNCS 458, p502-520, 1990.

....techniques in Section 0.3 have been adapted to real time. For automated theorem proving, the applicability for timed settings has been explored, e.g. in [Sha93] For process algebras, a number of calculi addressing time as a primitive exist. Examples for this are Timed CSP [RR88] TCCS [Yi90], and ATP [NS94] For stepwise refinement, time settings have been explored, e.g. in [SZJ94] For abstract interpretation, approximation of real time safety properties can be formulated in the have been formulated in this framework [WT94, DT98] An approach to approximate also liveness is ....

....Passed are reachable in M . Proof: This property holds by induction. Observe that all symbolic states inserted in Passed (line 5) have been in Waiting before. They are inserted in lines (1,9) In line 1, the initial configuration ( l 0 , e 0 , D 0 ) and all the configurations reachable via delaying, 0 ) are certainly reachable. The symbolic state l # , e # , D # ) is constructed by (symbolically) taking a transition l # , where every configuration represented by ( l # , e # , D # ) has by induction a reachable predecessor. Thus also every configuration in ( # l # , e # , D ## ) is ....

Wang Yi. Real-Time Behaviour of Asynchronous Agents. In J. C. M. Baeten and J. W. Klop, editors, CONCUR '90: Theories of Concurrency: Unification and Extension, volume 458 of Lecture Notes in Computer

....address this problem in this paper. In the untimed setting, bisimulation equivalences have been reasonably successful as notions of implementation between transition systems [6, 34] Consequently, bisimulation equivalences have also been proposed as implementation relations for the timed setting [4, 23, 35, 38, 47]. However, we do not believe that bisimulations will turn out to be very useful as implementation relations in the timed case. The problem is that they do not allow one to abstract in specifications from the often very complex timing behavior of implementations (see Chapter 10 of [23] for an ....

....that can block the passage of time, and a RATE operation that can change the speed of its argument. On the other hand, there are several operators that have been proposed in the literature that do not fit our format of action transducers, in particular, the CCS style choice operation present in [4, 35, 38, 47]. This operation cannot be expressed as a timed action transducer because the timed trace inclusion relation is not substitutive with respect to it. We briefly consider the design of an appropriate language of operators for describing timing based systems. Such a language should consist of a ....

[Article contains additional citation context not shown here]

Wang Yi. Real-time behaviour of asynchronous agents. In Baeten and Klop [5], pages 502--520. 44

....in the second argument of a timeout operator. The operational semantics of ASTPD associates labeled transition systems to processes. States are process expressions. Since the time domain is not necessarily IN, we cannot use the time action , as in [NS90] for temporal transitions. We use, as in [Wan90, MT90], transition systems labeled by L = A [ D 3 . The transition relation is then a subset of ASTP2 L 2ASTP. It is defined by structural induction, a la Plotkin [Plo81] by the following rules, where d; d 2 D 3 and l 2 L. ffi ffi P [ recX 1 P ) X] recX 1 P ff P e ff P ....

....8l; 8P ) 9Q 8l; 8Q ) 9P We write (P ) D to denote the model of P in the semantics of ASTPD . 2.2. 3 Properties of the models The transition relation satisfies the following properties, where d and d range over D 3 (the terminology used for (1) and (2) is due to Wang [Wan90]) 1) time determinacy: P ) P = P (where = is syntactic equality) 2) time continuity: P ) P (3) partial persistency: P 0) 8ff) 8P ) 8d 2]0; d [ 9P 1 ; P 2 ) P A process P is said to be immediate if it cannot let time progress, i.e. ....

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, LNCS 458, proceedings of CONCUR '90 (Theories of Concurrency: Unification and Extension), Amsterdam, The Netherlands, pages 502--520, Springer Verlag, August 1990.

.... I II) and as [43] 1 Introduction Most of the existing semantic models, languages and logics for describing and reasoning about timing based systems implicitly view an execution as an alternating sequence of instantaneous discrete actions and continuous phases during which time advances [2, 5, 7, 8, 9, 11, 14, 17, 20, 25, 26, 27, 48, 50, 52, 54, 61, 62]. To each system described in any of these formalisms one can associate a transition system or automaton consisting of (1) a set of states, 2) a set of initial states, 3) a set of discrete actions, 4) a set of discrete steps s Gamma s asserting that from state s the system can ....

....believe that timed automata, defined in this way, provide an excellent basis for defining and studying behavioral preorders and simulation proof techniques for timing based systems. Since timed automata can be viewed as an underlying semantic domain for any of the models, languages and logics of [2, 5, 7, 8, 9, 11, 14, 17, 20, 25, 26, 27, 48, 50, 52, 54, 61, 62], all the results that we obtain for timed automata carry over directly to those settings. For convenience, we use R as our domain of times in this paper. The need for densetime models has been well discussed in [4] However, for the purpose of generality we could have parameterized our timed ....

[Article contains additional citation context not shown here]

Wang Yi. Real-time behaviour of asynchronous agents. In Baeten and Klop [10], pages 502--520.

....theory has recently been devoted to the development of extensions of standard process algebras like CCS [16] CSP [11] and ACP [3] with constructs allowing for the modelling of timing aspects in the behaviour of processes. By now, most process algebras have a timed counterpart (see, e.g. [1, 6, 18, 21]) and the development of results and techniques for these languages is becoming comparable with that for the standard process description languages. For example, complete axiomatizations of behavioural On leave from School of Cognitive and Computing Sciences, University of Sussex, Brighton BN1 ....

....of process is at least as elegant and mathematically tractable as that of language. The main purpose of this paper is to show that the techniques developed by Milner in [15, 17] can be adapted to provide a complete axiomatization of the notion of timed bisimulation equivalence, due to Wang Yi [21], over a class of regular timed CCS processes [12, 22] More precisely, we shall offer a complete axiomatization of timed bisimulation over the language of action guarded regular expressions studied in [12] This complete axiomatization is obtained by combining an improved version of the laws ....

[Article contains additional citation context not shown here]

Wang Yi. Real-time behaviour of asynchronous agents. In Baeten and Klop [2], pages 502--520.

....the actions of gate closing and Basic Research in Computer Science, Centre of the Danish National Research Foundation. train crossing. Formal models for such so called real time systems have been studied intensively over the past decade, e.g. the timed automata [AD90] timed process algebras [Wan90] timed nets [LPY95] and timed Petri Nets 95] Much of the theory of untimed systems has been lifted successfully to these models of real time behavior of systems. As examples, many results from automata theory apply also to timed automata, AD90, AD94, ACM97] and a number of timed versions ....

.... automata, AD90, AD94, ACM97] and a number of timed versions of classical speci cation logics have been studied, AH91, LLW95] In this paper we focus on the classical notion of bisimulation [Mil89] which has already been introduced and studied for real time models by many researchers, e.g. in [Wan90, AKLN95, NSY93, AM94] A large part of the elegant theory of bisimulation for transition systems and reactive languages has been lifted to the real time setting. As an example, bisimulation was shown decidable for nite timed transition systems by Cer ans [ Cer92] and ecient algorithms ....

Y. Wang. Real-time behaviour of asynchronous agents. Proc. of CONCUR'90, LNCS 458, 1990.

.... formulae for finite state systems has been described in [Hil87, Cle90, Kor91, CC92, Pol92] and implemented in at least two tools [GLZ89, CPS89] During the last few years a number of real time process algebras has been introduced in order to handle quantitative aspects of processes [DS89, Wan90, NRSV90, BB89, Che91] In addition a number of time sensitive and time abstracting (bi)simulation equivalences and preorders has been introduced and studied [Wan90, LW90, GL92, DS89] Due to the use of the non negative reals as time domain, even the simplest processes describe infinite states ....

.... few years a number of real time process algebras has been introduced in order to handle quantitative aspects of processes [DS89, Wan90, NRSV90, BB89, Che91] In addition a number of time sensitive and time abstracting (bi)simulation equivalences and preorders has been introduced and studied [Wan90, LW90, GL92, DS89] Due to the use of the non negative reals as time domain, even the simplest processes describe infinite states systems. Thus, decidability of (bi)similarity cannot be achieved using the standard algorithmic techniques for finite state systems. However, decidability of ....

[Article contains additional citation context not shown here]

Y. Wang. Real--time behaviour of asynchronous agents. In Proceedings of CONCUR'90, volume 458 of Lecture Notes In Computer Science, Springer Verlag. Springer-Verlag, 1990.

....Intuitively, the more must transitions and the fewer may transitions a specification has, the finer it is. Also, we introduce notions of refinements abstracting from time and or internal computation. TMS specifications may be combined with respect to the constructs of the real time calculus [Wan90]. Time sensitive notions of refinements that are preserved by these constructs are defined , thus enabling compositional verification. Epsilon provides automatic tools for verifying refinements. We apply Epsilon to a compositional verification of a train crossing example. 1 ....

....[GLZ89, BLS92] During the last few years various process calculi have been extended to include real time in order to handle quantitative aspects of real time systems, for instance that some critical event must not or should happen within a certain time period. We mention the calculi defined in [Wan90] and the ones defined in [NSY91] and [BB89] Common to these real time calculi is that time is represented by some dense time domain, e.g. the non negative reals. This work has been supported by the Danish National Science Research Council project DART and the ESPRIT Basic Research Action ....

[Article contains additional citation context not shown here]

Y. Wang. Real--time behaviour of asynchronous agents. In Proceedings of CONCUR'90, volume Recent BRICS Report Series Publications RS-97-11 K arlis Cer ans, Jens Chr. Godskesen, and Kim G. Larsen. Timed Modal Specification --- Theory and Tools. April

....of a beautiful argument due to Hennessy [10] This first behavioural characterization applies, e.g. to transition systems with an uncountable action set like those that arise in timed process calculi which postulate the positive real numbers as their time domain. cf. e.g. Wang s TCCS [33]. We then concentrate our attention on transition systems over a countable action set. For several classes of such transition systems (viz. the class of all such transition systems, the class of those which have bounded convergent sort, the sort finite transition systems and those that are image ....

....example, it can be used as an observation independent version of . over lts s with an uncountable action set. This means, in particular, that such a characterization applies to the bisimulation preorder for, e.g. timed calculi which postulate an uncountable time domain like, e.g. Wang s TCCS [33]. However, the lts s giving operational semantics to most standard process calculi, e.g. those for ACP [8] CCS [24] and CSP [14] have countable action sets. For such transition systems, it is possible to give an alternative characterization of the preorder . which 17 is, in many ways, ....

Y. Wang, Real-time behaviour of asynchronous agents, in Proceedings CONCUR 90, Amsterdam, J. Baeten and J. Klop, eds., vol. 458 of Lecture Notes in Computer 29 Recent Publications in the BRICS Report Series RS-95-59 Luca Aceto and Anna Ing olfsd ottir. On the Finitary Bisimulation. November

....automatic reasoning. The theory of TMS is a real time extension of Modal Specifications [Lar90, BL90, LT88, HL89] which in turn is an extension of process algebras, such as CCS. The real time extension of Modal Specifications is inspired by the real time extension of CCS by Wang presented in [Wan90]. To illustrate the design principles and the philosophy underlying the theory of TMS consider the following example. The specification of P x below is a description of a perfect medium with a transmission delay x. Intuitively, we have that a message must be accepted at any time. This is denoted ....

.... Gamma Gamma being attached precisely x time units after the point at which the arrow head of Gamma Gamma reaches the second horizontal line. That is, the delay x is relative to the occurrence of the acc event. Applying the syntax of TMS [ CGL93] which is an extension of Wang s TCCS [Wan90] we write = acc:ffl(x) del:P x in order to express the perfect medium. Using a similar diagrammatic representation we define a faulty medium F x;y with transmission delay x and enforced timeout at y. Intuitively, the faulty medium behaves exactly as the perfect medium P x except that y del ....

Y. Wang. Real--time behaviour of asynchronous agents. In Proceedings of CONCUR'90, volume 458 of Lecture Notes in Computer Science. Springer-Verlag,

....it is shown that the model checking problem for ERL , and therefore also for ERL , is decidable. In the framework of event recording automata 4 and ERL we present the construction of characteristic formulas for two behavioral relations, timed bisimilarity, as introduced by Wang Yi [Yi90] and timed similarity, a real time version of the Milner simulation relation [Mil71] In both cases the size of the formulas is linear with respect to the size of the corresponding event recording automaton. The results show that the event recording logic with greatest xpoints is expressive ....

....0 ) i there is an edge hl; l 0 ; a; gi such that v satis es g and v 0 = v[S(a) 0] 2.3 Timed Behavioral Relations We introduce now two behavioral relations over timed labeled transition systems (TLTSs) which we study in this paper. The notion of timed bisimulation was introduced by Wang [Yi90]. De nition 7 (Timed Simulation Timed Bisimulation) Given a timed labeled transition system T = hQ; Q 0 ; IR 0 ; i. A timed simulation is a relation R Q Q such that whenever q 1 Rq 2 and 2 [ IR 0 then 11 Whenever q 1 q 0 1 then there exists q 0 2 such that q 2 ....

Wang Yi. Real-time behaviour of asynchronous agents. In J. C. M. Baeten and J. W. Klop, editors, CONCUR '90: Theories of Concurrency: Unication and Extension, volume 458 of Lecture Notes in Computer Science, pages 502-520. Springer-Verlag, 1990. 49

....is a great demand for formal methods applicable to real time systems. Developing formal methods for the design and analysis of real time systems is a very active area of current research. Several different formalisms have been proposed. These include timed Petri Nets [4] timed process algebras [9, 10, 6], real time temporal logics [2, 5] and timed automata [1] Moreover, there is a pressing need to develop efficient tools to be embedded in a real time software development process. Timed algebras are process algebras extended with a set of constructs to express timing requirements. They have ....

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, CONCUR 90: Theories of Concurrency, Lecture Notes in Computer Science 458, Springer-Verlag, 1990.

....s 2 S such that s a s. As usual, we write s to mean that there is some state s 0 such that s s 0 , and s 6 if there is no state s 0 such that s s 0 . The axioms of time determinism, time additivity and 0 delay are standard in the literature on TCCS (see, e.g. [9]) Those dealing with urgent actions are motivated by the particular kind of timed automaton model considered in veri cation tools like HyTech [5] and Uppaal [8] A delaying computation is a sequence of transitions s 0 1 s 1 2 : n s n (n 0) such that i = or i 2 D, for ....

....are motivated by the particular kind of timed automaton model considered in veri cation tools like HyTech [5] and Uppaal [8] A delaying computation is a sequence of transitions s 0 1 s 1 2 : n s n (n 0) such that i = or i 2 D, for every i 2 f1; ng. Following [9], we now proceed to de ne versions of the transition relations that abstract from the internal evolution of states as follows: s a = s 0 i 9s 00 : s s 00 a s 0 s (d) s 0 i there exists a delaying computation s = s 0 1 s 1 2 : n s n = s 0 with ....

[Article contains additional citation context not shown here]

Y. Wang, Real-time behaviour of asynchronous agents, in Proc. of the Conference on Theories of Concurrency: Unication and Extension, CONCUR'90, J. Baeten and J. Klop, eds., vol. 458 of Lecture Notes in Computer Science, Amsterdam, The Netherlands, August 2730

....nature. Research on all these quantitative extensions of process algebras started around the same time. 2.1 Timed process algebras Timed extensions of process algebras have received considerable attention in the last decade. To mention a few, extensions of languages like ACP [5] CSP [92] CCS [80,104] and LOTOS [15,75] have been defined. The main idea of these calculi is to extend the language with a timed prefix like (t) P which denotes that process P is reached after a delay of t time units. Both discrete time and real time variants are considered, depending on the domain of t. A main ....

....but during which no actions happen. The resulting calculus is a proper extension of classical process algebras and the algebra for describing CTMCs, MC (cf. Section 4) We will show that this separation which is also applied in several timed process algebras like TCCS [80] Temporal CCS [104] and Timed CSP [92] results in a synchronisation scheme that corresponds to the aforementioned intuition. In the context of Markovian process algebras, this separation has been brought up by Hermanns and Rettelbach [55] and has been worked out in [47] 7.1 Syntax The syntax of the algebra IMC ....

Y. Wang. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J-W. Klop, eds, Concur'90: Theories of Concurrency -- Unification and Extension, LNCS 458, pages 502--520, 1990.

....As usual, we write s ff Gamma to mean that there is some state s 0 such that s ff Gamma s 0 , and s 6 ff Gamma if there is no state s 0 such that s ff Gamma s 0 . The axioms of time determinism, time additivity and 0 delay are standard in the literature on TCCS (see, e.g. [9]) Those dealing with urgent actions are motivated by the particular kind of timed automaton model considered in verication tools like HyTech [5] and Uppaal [8] A delaying computation is a sequence of transitions s 0 ff 1 Gamma s 1 ff 2 Gamma : ff n Gamma s n (n 0) such that ff ....

....the particular kind of timed automaton model considered in verication tools like HyTech [5] and Uppaal [8] A delaying computation is a sequence of transitions s 0 ff 1 Gamma s 1 ff 2 Gamma : ff n Gamma s n (n 0) such that ff i = or ff i 2 D, for every i 2 f1; ng. Following [9], we now proceed to dene versions of the transition relations that abstract from the internal evolution of states as follows: s a = s 0 ioe 9s 00 : s Gamma s 00 a Gamma s 0 s ffl(d) s 0 ioe there exists a delaying computation s = s 0 ff 1 Gamma s 1 ff 2 Gamma : ....

[Article contains additional citation context not shown here]

Y. Wang, Real-time behaviour of asynchronous agents, in Proc. of the Conference on Theories of Concurrency: Unication and Extension, CONCUR'90, J. Baeten and J. Klop, eds., vol. 458 of Lecture Notes in Computer Science, Amsterdam, The Netherlands, August 2730 1990, Springer-Verlag, pp. 502520.

....of actions at the same point in time. We introduce different equivalence relations based on bisimulation. 1 Introduction Real time models are used to model time dependent physical problems. The common approach is to restrict action occurrences to closed, more precisely to left closed intervals [RR88, Sch00, MT90, Wan90, Mur92, FZ94, CL96, LL97]. Contrary to this, timed automata [AD94] and some process algebras [BB91, Klu91, Dan91, Che92, Jef92] allow actions to occur in open intervals in order to increase their expressive power. Another important property of timed process algebras is the maximal progress assumption, i.e. an action must ....

....of timed process algebras is the maximal progress assumption, i.e. an action must occur at the instant at which all participants are ready. This assumption thus guarantees that time cannot proceed if an internal action is enabled. Typical time process algebras which meet this assumption are [HR95, Wan90, Sch00, CL96, LL97]. But none of the mentioned algebras satisfy both properties. In [Dan91] the author considered a progress assumption, which means that an internal action must not be delayed more than to its upper time limit, i.e. it is not allowed to disable an internal action by idling. His assumption is ....

[Article contains additional citation context not shown here]

Y. Wang. Real-time behaviour of asynchronous agents. LNCS, 458:502--520, 1990.

....the flows by an OR rule, the resource static interval of the ressource has to be ( 1; 0) which is not possible. That is why we introduce [ Delta] 3. 4 Equivalence It is known that bisimulation ( 13] is a good tool for comparing models, leading for timed systems, to a timed bisimulation [16, 10]. 16] use bisimulation for Timed CCS, and (like many others) splits events in actions (a or ) and delay (ffl(t) In TPNs and TSPNs, each action occurs at a time (but delay and action time are equivalent, has said in [1, p3] Definition 3.14 (Labeled Timed Transition System) A Labeled Timed ....

....flows by an OR rule, the resource static interval of the ressource has to be ( 1; 0) which is not possible. That is why we introduce [ Delta] 3. 4 Equivalence It is known that bisimulation ( 13] is a good tool for comparing models, leading for timed systems, to a timed bisimulation [16, 10] [16] use bisimulation for Timed CCS, and (like many others) splits events in actions (a or ) and delay (ffl(t) In TPNs and TSPNs, each action occurs at a time (but delay and action time are equivalent, has said in [1, p3] Definition 3.14 (Labeled Timed Transition System) A Labeled Timed ....

Y. Wang. Real-time behaviour of asynchronous agents. In J. C. M. Baeten and J. W. Klop, editors, Proceedings of CONCUR'90, volume 458 of Lecture Notes in Computer Science, pages 502--520, Amsterdam, The Netherlands, 27-- 30Aug. 1990. Springer-Verlag.

....address this problem in this paper. In the untimed setting, bisimulation equivalences have been reasonably successful as notions of implementation between transition systems [6, 34] Consequently, bisimulation equivalences have also been proposed as implementation relations for the timed setting [4, 23, 35, 38, 46]. However, we do not believe that bisimulations will turn out to be very useful as implementation relations in the timed case. The problem is that they do not allow one to abstract in specifications from the often very complex timing behavior of implementations (see Chapter 10 of [23] for an ....

....that can block the passage of time, and a RATE operation that can change the speed of its argument. On the other hand, there are several operators that have been proposed in the literature that do not fit our format of action transducers, in particular, the CCS style choice operation present in [4, 35, 38, 46]. This operation cannot be expressed as a timed action transducer because the timed trace inclusion relation is not substitutive with respect to it. We briefly consider the design of an appropriate language of operators for describing timingbased systems. Such a language should consist of a small ....

[Article contains additional citation context not shown here]

Wang Yi. Real-time behaviour of asynchronous agents. In Baeten and Klop [5], pages 502--520.

....the capabilities of the language. The complete concrete and abstract syntax of mosca is given in [15] together with a formal semantics, based on the dynamic semantic model for VDM SL [9] and Plotkin s labelled transitions systems [13] extended to handle time in a manner inspired by Wang Yi s work [17]. The basic element in the mosca model is a process, which is called agent. In the following two sections an overview is presented of the various kind of attributes a standard process can obtain through various definitions. Section 2 shows some of the constructs available for agent behaviour ....

Y. Wang. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, CONCUR'90 Theories of Concurrency: Unification and Extension, volume 458 of LNCS, pages 502--520. Springer Verlag, 1990. 15

....often called the maximal progress assumption. Our format is inspired by TPL [HeR91] which was in turn influenced by [Phi89] It is a subformat of SF, where we make a restriction on the s rules. Apart from TPL, other timed process algebras have been proposed in [ReR88] BaB91] NRSV90] MoT90] [Wan90] among others. DEFINITION 4.1 (Timed format) Let a language definition S have action set A containing special actions t, s. Then S is in timed format (TF) if it is in SF and satisfies the following further conditions: 1) s may not appear in either the premises or conclusion of a DeS rule. 2) ....

Wang Yi. Real-time behaviour of asynchronous agents. CONCUR '90. LNCS 458 (502-520). Springer, 1990. 11/7/97 14

....which is a main result of [LY93] Related work There have been few comparisons of timed CCS with prioritised CCS. However, Jef92b] gives a translation of timed algebra into a prioritised algebra where every action is time stamped. Some confusion surrounds the expansion theorem for timed CCS [GL92, Hen92, Yi90, Yi91]. The situation seems to be that if a time out operator is used and time is discrete, an expansion theorem is possible. In CCS, the delay operator can be derived from the time out. An expansion theorem is awkward with the delay operator regardless of the density of time. For dense time, an ....

Wang Yi. Real time behaviour of asynchronous agents. In CONCUR'90, 1990. Springer Verlag LNCS 458.

....algorithms for deciding various equivalences and refinements between specifications in TMS. The report does not contain a detailed presentation of TMS, for that purpose we refer the reader to [ CGL93, GLS93] For a presentation of TCCS, upon which TMS is based, we refer the reader to [LW90, Wan90, Wan91] The report is organized as follows. The next section we explain how to get Epsilon and how to make the system run. In Section 3 we define the Epsilon syntax of TMS and give a few examples. In Section 4 we provide the predicates for deciding various (timed) bisimulation equivalences and ....

Y. Wang. Real--time behaviour of asynchronous agents. In Proceedings of CONCUR'90, volume 458 of Lecture Notes in Computer Science. Springer-Verlag, 1990.

....real time versions of ACP presented in [6] unlike those presented in [2] and [3] do not exclude the possibility of two or more actions to be performed consecutively at the same point in time. That is, they include urgent actions, similar to ATP [19] and the different versions of CCS with timing [11, 18, 21]. This feature seems to be essential to obtain simple and natural embeddings of discrete time versions as well as useful in practice when describing and analyzing systems in which actions occur that are entirely independent. This is, for example, the case for actions that happen at different ....

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, CONCUR'90, pages 502--520. LNCS 458, Springer-Verlag,

....well as new timed process algebras. CSP [Hoa 85] CCS [Mil 89] ACP [BeK 85] LOTOS [ISO 8807] have been extended to Timed CSP [ReR 88, Ree 90] TCCS (Temporal CCS) MoT 89] TIC [QAF 89] ACP r [BaB 90] CELOTOS [HTZ 90] ACP t te [Gro 90] Timed Interaction LOTOS [BLT 90, BoL 91] Timed CCS [Wan 90, Wan 91] and TPCCS [HaJ 90, Han 91] New process algebras have been proposed which are intended to model time in a quantitative way: first, synchronous process algebras such as SCCS [Mil 83] Meije [AuB 85] or CIRCAL [Mil 85] and, in a second step, timed process algebras such as TPL (Temporal ....

....briefly compare our proposal with previous works on timed extensions in several process algebras, including LOTOS. We will start with the approaches which are the closest to ours (ATP [NS 90] TPL [HeR 90b] ACP t te [Gro 90] TCCS [MoT 89] PADS [Azc 90] Timed CSP [ReR 88, Ree 90] Timed CCS [Wan 90, Wan 91] and TPCCS [Han 91] and compare the differences between the basic choices in the semantics of the operators (see table below) The LOTOS parallel composition operator is specific, and our work cannot be strictly compared with others. For instance, in TPL and TCCS, the parallel ....

Y. Wang, Real-Time Behaviour of Asynchronous Agents, in: J.C.M. Baeten, J.W. Klop, eds., CONCUR '90, Theories of Concurrency: Unification and Extension, LNCS 458 (Springer - Verlag, Berlin Heidelberg New York, 1990, ISBN 3-540-53048-7) 502-520.

.... 90] ACP t te [Gro 90] ATP (Algebra of Timed Processes) NRS 90, NiS 91, NSY 91] 1 , CIRCAL [Mil 85] Estelle [ISO 9074] LOTOS T [MFV 92] Meije [AuB 84] PADS (Process Algebra for Distributed Systems) Azc 90] SCCS [Mil 83] SDL [CCITT Z100] TCCS [MoT 90] TIC [QAF 90] TiCCS (Timed CCS) Wan 90, Wan 91] TiCSP (Timed CSP) ReR 88, Ree 90] Timed arc PN [Wal 83] Timed PN [MeF 76] TinLOTOS (TimedInteraction LOTOS) BLT 90] TLOTOS [Led 92] Timed LOTOS [LeL 92] ULOTOS T LOTOS [BoL 92] TPCCS [Haj 90, Han 91] TPL (Temporal Process Language) HeR 91] As we can see, there exist many ....

Y. Wang, Real-Time Behaviour of Asynchronous Agents, in: J.C.M. Baeten, J.W. Klop, eds., CONCUR '90, Theories of Concurrency: Unification and Extension, LNCS 458 (Springer - Verlag, Berlin Heidelberg New York, 1990) 502-520.

.... list of them are referred to by the following acronyms in the sequel: ACP r [BaB 90] ACP t te [Gro 90a] ATP (Algebra of Timed Processes) NRS 90, NiS 91b, NSY 91] LOTOST [MFV 92] PADS (Process Algebra for Distributed Systems) Azc 90] TCCS (Temporal CCS) MoT 90] TIC [QAF 89] Timed CCS [Wan 90, Wan 91] Timed CSP [ReR 88, DaS 89, Ree 90] Timed interaction LOTOS [BLT 90] TLOTOS [Led 92] T LOTOS and ULOTOS [BoL 92] TPCCS (Timed Probabilistic CCS) HaJ 90, Han 91] TPL (Temporal Process Language) HeR 90] An overview and synthesis on Timed Process Algebras may be found in [NiS 91a] ....

Y. Wang, Real-Time Behaviour of Asynchronous Agents, in: J.C.M. Baeten, J.W. Klop, eds., CONCUR '90, Theories of Concurrency: Unification and Extension, LNCS 458 (Springer - Verlag, Berlin Heidelberg New York, 1990) 502-520.

....to develop it. Different from the real time versions of [2] and [4] this version does not exclude the possibility of two or more actions to be performed consecutively at the same point in time. That is, it includes urgent actions, similar to ATP [37] and the different versions of CCS with timing [19, 35, 44]. This is useful in practice when describing and analyzing systems in which actions occur that are entirely independent. This is, for example, the case for actions that happen at different locations in a distributed system. In [2] and [4] the main idea was that it is difficult to imagine that ....

....see e.g. 12] 14] and [17] We did not give explicit consideration to other algebraic concurrency theories that deal with time dependent behaviour. In general, they have urgent actions and relative timing. This is, for example, the case with ATP [37] the different versions of CCS with timing [19, 35, 44] and TIC [39] TIC is rooted in LOTOS [46] We claim, on the basis of the connections described in [6] that there are indeed close connections between these theories and the versions of ACP with relative timing presented in this chapter, i.e. ACP srt and ACP drt . We also claim that there ....

[Article contains additional citation context not shown here]

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, CONCUR'90, pages 502--520. LNCS 458, Springer-Verlag, 1990.

....to develop it. Di erent from the real time versions of [2] and [4] this version does not exclude the possibility of two or more actions to be performed consecutively at the same point in time. That is, it includes urgent actions, similar to ATP [37] and the di erent versions of CCS with timing [19, 35, 44]. This is useful in practice when describing and analyzing systems in which actions occur that are entirely independent. This is, for example, the case for actions that happen at di erent locations in a distributed system. In [2] and [4] the main idea was that it is dicult to imagine that actions ....

....see e.g. 12] 14] and [17] We did not give explicit consideration to other algebraic concurrency theories that deal with time dependent behaviour. In general, they have urgent actions and relative timing. This is, for example, the case with ATP [37] the di erent versions of CCS with timing [19, 35, 44] and TIC [39] TIC is rooted in LOTOS [46] We claim, on the basis of the connections described in [6] that there are indeed close connections between these theories and the versions of ACP with relative timing presented in this chapter, i.e. ACP srt and ACP drt . We also claim that there is ....

[Article contains additional citation context not shown here]

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, CONCUR'90, pages 502-520. LNCS 458, Springer-Verlag, 1990.

....to develop it. Di erent from the real time versions of [1] and [3] this version does not exclude the possibility of two or more actions to be performed consecutively at the same point in time. That is, it includes urgent actions, similar to ATP [30] and the di erent versions of CCS with timing [16, 28, 35]. This is useful in practice when describing and analyzing systems in which actions occur that are entirely independent. This is, for example, the case for actions that happen at di erent locations in a distributed system. In [1] and [3] the main idea was that it is dicult to imagine that actions ....

....see e.g. 10] 12] and [14] We did not give explicit consideration to other algebraic concurrency theories that deal with time dependent behaviour. In general, they have urgent actions and relative timing. This is, for example, the case with ATP [30] the di erent versions of CCS with timing [16, 28, 35] and TIC [32] TIC is rooted in LOTOS [37] We claim, on the basis of the connections described in [5] that there are indeed close connections between these theories and the versions of ACP with relative timing presented in this paper, i.e. ACP srt and ACP drt . We also claim that there is a ....

[Article contains additional citation context not shown here]

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, CONCUR'90, pages 502-520. LNCS 458, Springer-Verlag, 1990.

....real time versions of ACP presented in [6] unlike those presented in [2] and [3] do not exclude the possibility of two or more actions to be performed consecutively at the same point in time. That is, they include urgent actions, similar to ATP [19] and the di erent versions of CCS with timing [11, 18, 21]. This feature seems to be essential to obtain simple and natural embeddings of discrete time versions as well as useful in practice when describing and analyzing systems in which actions occur that are entirely independent. This is, for example, the case for actions that happen at di erent ....

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, CONCUR'90, pages 502-520. LNCS 458, Springer-Verlag,

....on broadcasting instead of handshake. These are examples of problem areas which have motivated various adaptations and extensions of process calculi, and of other theories as well. CCS has due to its simple and elegant mathematical framework proven to be an appropriate basis for several timed [HR90, MT90, NS91, W90, W91, W91b] and probabilistic formalisms [JL91, LS88] and a new calculus based on the broadcast paradigm [Pr91, Pr93v, Pr93p] One could well say that a process calculus can favourably be used as a test bench for experiments with various adaptations, not only as a fixed formalism. An interesting and ....

Wang, Y., Real Time Behaviour of Asynchronous Agents, in Baeten, J.C.M. and Klop, J.W., editors, proceedings from CONCUR'90, LNCS 458, Springer Verlag, 1990.

....PROPERTIES OF REGULAR REAL TIMED PROCESSES UNO HOLMER, KIM LARSEN, WANG YI June 7, 1991 Abstract. We discuss the decidability problem associated with verifying properties of processes expressed in the real time process calculus TCCS of [W90]. A regular subcalculus TC of TCCS is considered. Two operational semantics, and associated timed notions of bisimulation, are given: a standard infinite semantics, and a symbolic finite semantics. The consistency between the two semantics is proved. We show that both the equivalences are ....

....13 3.3. Extended Timed Modal Logic 16 4. Conclusion and Future Work 18 References 18 DECIDING PROPERTIES OF REGULAR REAL TIMED PROCESSES 3 1. Motivation Recently, numerous models within the frameworks for timed processes based on process calculi and temporal logic have been developed [ACD90, AD90, HR90, MT90, RR86, S90, W90]. In this paper, we discuss the decidability problem associated with verifying properties of processes expressed in the real time process calculus TCCS of Wang [W90] As the specification language for expressing such properties one may choose to use the timed calculus itself, with the notion of ....

[Article contains additional citation context not shown here]

Y. Wang, Real Time Behaviour of Asynchronous Agents, LNCS 458, 1990.

....As usual, we write s ff Gamma to mean that there is some state s 0 such that s ff Gamma s 0 , and s ff Gamma if there is no state s 0 such that s ff Gamma s 0 . The axioms of time determinism, time additivity and 0 delay are standard in the literature on TCCS (see, e.g. [22]) Those dealing with urgent actions are motivated by the particular kind of timed automaton model considered in veri cation tools like HyTech [9] and Uppaal [5] A delaying computation is a sequence of transitions s 0 ff 1 Gamma s 1 ff 2 Gamma : ff n Gamma s n (n 0) such that ff ....

....particular kind of timed automaton model considered in veri cation tools like HyTech [9] and Uppaal [5] A delaying computation is a sequence of transitions s 0 ff 1 Gamma s 1 ff 2 Gamma : ff n Gamma s n (n 0) such that ff i = or ff i 2 D, for every i 2 f1; ng. Following [22], we now proceed to de ne versions of the transition relations that abstract from the internal evolution of states as follows: s a = s 0 ioe 9s 00 : s Gamma s 00 a Gamma s 0 s ffl(d) s 0 ioe there exists a delaying computation s = s 0 ff 1 Gamma s 1 ff 2 Gamma ....

[Article contains additional citation context not shown here]

Y. Wang, Real-time behaviour of asynchronous agents, in Proc. of the Conference on Theories of Concurrency: Uniøcation and Extension, CONCUR'90, J. Baeten and J. Klop, eds., vol. 458 of Lecture Notes in Computer Science, Amsterdam, The Netherlands, August 2730 1990, Springer-Verlag, pp. 502 520.

....are equivalent modulo timing behaviour. Thus one process may be used to specify simply the functional behaviour of a system by requiring that any proposed implementation should be time abstracting bisimilar to it. They prove that time abstracting equivalence is decidable for a timed CCS calculus [Wan90], in contrast to the refinement relation presented in this paper, which is not decidable. Interestingly, they also establish that time abstracting congruence (i.e. equivalence in all contexts) is standard timed bisimulation. The corresponding result for this paper is that untimed traces ....

Wang Yi, Real-time behaviour of asynchronous agents, Proceedings of CONCUR '90, LNCS 458, 1990. A Semantic models and functions Traces The traces model MUT is defined to be those sets of traces that are non-empty, and closed under prefixing. They are ordered under set containment.

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In Concurrency Theory, volume 458 of Lect. Notes in Comp. Sci., pages 502-520. Springer, 1990. 15

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, Proceedings CONCUR 90, Amsterdam, volume 458 of Lecture Notes in Computer Science, pages 502--520. Springer-Verlag, 1990. 23

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In Baeten and Klop

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In Concurrency Theory, volume 458 of Lect. Notes in Comp. Sci., pages 502--520. Springer, 1990. 15

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, Proceedings CONCUR 90, Amsterdam, pages 502--520, SpringerVerlag, 1990.

No context found.

Y. Wang. Real-time behaviour of asynchronous agents. In Proc. CONCUR 1990, volume 458 of LNCS, pages 502--520. Springer-Verlag, August 1990.

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In Proc. 1st International Conference on Theory of Concurrency (CONCUR'90), volume 458 of Lecture Notes in Computer Science, pages 502--520. Springer, 1990.

No context found.

Wang Yi, Real-time behaviour of asynchronous agents, in: J.C.M. Baeten, J.W. Klop (Eds.), CONCUR'90, Lecture Notes in Computer Science, vol. 458, Springer, Berlin, 1990, pp. 502--520.

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In Proc. CONCUR'90, pages 502-520, 1990.

No context found.

Wang Yi. Realtime behaviour of asynchronous agents. In Proceedings of the International Conference on Concurrency Theory (CONCUR'90), number 458 in LNCS. SpringerVerlag, 1990.

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In Proc. CONCUR'90, pages 502-520, 1990.

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In J.C.M. Baeten and J.W. Klop, editors, Proceedings CONCUR 90, Amsterdam, volume 458 of Lecture Notes in Computer Science, pages 502--520. Springer-Verlag, 1990.

No context found.

Wang Yi. Real-time behaviour of asynchronous agents. In Baeten and Klop

First 50 documents  Next 50

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC