R. Cleaveland, G. Luttgen, and V. Natarajan. A process algebra with distributed priorities. [MS96], 34--49. (p 18)  Home/Search   Document Details and Download   Summary   Related Articles   Check

....talking about equivalence between CPG processes, for example, Sys = P . This is to be interpreted as o . 9. Logic We brie y consider Hennessy Milner style logics for specifying properties of CPG processes. Such logics have previously been de ned for a distributed prioritised process algebra [CLN98, Lt98]. Our starting point is the logic for CCS de ned by Hennessy and Milner [HM85, Mil89] This allows us to describe properties which processes may enjoy. For instance haiT would mean can do action a . In our setting, actions are conditional on the environment eschewing certain actions, and so it is ....

R. Cleaveland, G. Lttgen, and V. Natarajan. A process algebra with distributed priorities. Theoretical Computer Science, 195(2):227258, 1998.

....talking about equivalence between CPG processes, for example, Sys = P. This is to be interpreted as o# #. 9. LOGIC We briefly consider Hennessy Milner style logics for specifying properties of CPG processes. Such logics have previously been defined for a distributed prioritised process algebra [CLN98, Lt98]. Our starting point is the logic for CCS defined by Hennessy and Milner [HM85, Mil89] This allows us to describe properties which processes may enjoy. For instance #a#T would mean can do action a . In our setting, actions are conditional on the environment eschewing certain actions, and so it ....

R. Cleaveland, G. Lttgen, and V. Natarajan. A process algebra with distributed priorities. Theoretical Computer Science, 195(2):227--258, 1998.

....work [BCL97] demonstrates that priorities can be an effective way of cutting down state explosion in model checking verification. At present, E Lotos has no concept of priorities, although the introduction of priorities was a goal of the Committee initially. As regards Lotos NT, based on [BCL97, CLN97] we propose to attach priorities to internal actions (using the hide operator to specify priorities) in such a way that prioritized actions can preempt other actions. There are two other important issues for which we seek a better solution than E Lotos: H. Garavel, M. Sighireanu ffl ....

R. Cleaveland, G. Luttgen, and V. Natarajan. A Process Algebra with Distributed Priorities. Theoretical Computer Science, 1997. To Appear.

....ways. Often such extensions have led to the necessity of introducing a notion of priority among actions which is useful, e.g. to model mechanisms of pre emption. The problems arising from expressing priority have been previously studied in the context of prioritized process algebras, see e.g. [5, 10, 3] and [4] for a survey. One of the open questions in this context (see [4] is nding a complete axiomatization for observational congruence in the presence of recursion. In [4] where process algebras with priority are studied in full generality, the authors show that it is necessary to consider ....

.... this has been studied also in [6] where actions represent non zero time delays, classical actions of CCS are executed in zero time, and the priority of actions over actions derives from the maximal progress assumption (i.e. the system cannot wait if it has something internal to do) As in [5, 10, 3, 4, 6] we assume that visible actions never have pre emptive power over lower priority actions, because we see visible actions as indicating only the potential for execution. On the other hand, as observed e.g. in [4] in the presence of a restriction operator this assumption is necessary to get the ....

R. Cleaveland, G. Luttgen, V. Natarajan, \A Process Algebra with Distributed Priorities", in Proc. of the 7th Int. Conf. on Concurrency Theory (CONCUR '96), LNCS 1119:34-49, 1996

....mentioned extensions are concerned, deal M. Mendler 3 July 21, 1999 Department of Computer Science, University of Sheffield with non distributed systems, i.e. with global time and global priorities. Only recently process algebras with distributed time and priorities have been introduced [CLM97, CLN96] Another characteristic of existing timed process algebras is that they are geared towards a maximally detailed and low level description of a system s temporal behaviour. For complex signal flow graphs this must inevitably lead to unmanageable descriptions. Because of this these timed process ....

R. Cleaveland, G. Luttgen, and V. Natarajan. A process algebra with distributed priorities. In CONCUR '96, pages 34--49, 1996.

....(WFAR) that allows to escape divergence only if a silent alternative exists. Fair testing equivalences have been developed in [33, 9] In recent years, CCS has been extended in different directions, among them priority and real time. Different prioritised process algebras have been developed [5, 11, 16, 34, 10, 38, 13]. Investigations of observational congruence in the presence of priority have been restricted to finite, i.e. recursion free processes [34] In that approach priority is nicely reflected by the following axiom, where a has a lower priority than b: P a:Q = P . A variety of timed process ....

....system for observational congruence for calculi with recursion including either priority or maximal 21 progress. The proof system for WFAR should allow to fill some of the existing gaps of incomplete proof systems. Of particular interest is weak prioritised bisimilarity of [34] and its successor [13]. Indeed, we have provided a complete proof system for CCS with priority modulo a simplified notion of prioritised observational congruence. It is well known that many strong and weak equivalences can be characterised by means of simple modal logic characterisations. We plan to investigate such ....

R. Cleaveland, G. Luttgen, and V. Natarjan. A Process Algebra with Distributed Priorities. In Proceedings CONCUR 96, Springer LNCS 1119:34-49,1996.

....(WFAR) that allows to escape divergence only if a silent alternative exists. Fair testing equivalences have been developed in [33, 9] In recent years, CCS has been extended in different directions, among them priority and real time. Different prioritised process algebras have been developed [5, 11, 16, 34, 10, 38, 13]. Investigations of observational congruence in the presence of priority have been restricted to finite, i.e. recursion free processes [34] In that approach priority is nicely reflected by the following axiom, where a has a lower priority than : P a:Q = P . A variety of timed process ....

....system for observational congruence for calculi with recursion including either priority or maximal progress. The proof system for WFAR should allow to fill some of the existing gaps of incomplete proof systems. Of particular interest is weak prioritised bisimilarity of [34] and its successor [13]. Indeed, we have provided a complete proof system for CCS with priority modulo a simplified notion of prioritised observational congruence. It is well known that many strong and weak equivalences can be characterised by means of simple modal logic characterisations. We plan to investigate such ....

R. Cleaveland, G. Luttgen, and V. Natarjan. A Process Algebra with Distributed Priorities. In Proceedings CONCUR 96, Springer LNCS 1119:34-49,1996.

....of deadlock) of concurrent systems could be investigated. Subsequently, the expressiveness of classical process algebras was enriched by allowing for the modeling of real world features such as priorities, probabilities and durations, thereby resulting in prioritized process algebras (see e.g. [4, 14, 13, 57, 17, 15]) probabilistic process algebras (see e.g. 47, 30, 58, 37, 34, 5, 56] deterministically timed process algebras (see e.g. 52, 3, 41, 51, 39, 20, 60, 23, 36, 19] and stochastically timed process algebras (see e.g. 42, 24, 27, 12, 2, 21, 53, 26, 11, 45, 25, 31, 46] The enhanced expressive ....

.... is explicitly defined, from the proposal of [57] where priority is expressed as extremal probability and the computation proceeds in locksteps, from CCSR [17] where priority is used to arbitrate between simultaneous resource requests and lockstep parallelism is considered, and from CCS prio [15], where actions are allowed to preempt others only at the same site so as to capture a notion of localized precedence. Finally, if we consider the features a prioritized process algebra should possess according to [57] we have that the priority relation of EMPA pt;w is globally dynamic, i.e. it ....

R. Cleaveland, G. Luttgen, V. Natarajan, "A Process Algebra with Distributed Priorities", in Proc. of the 7th Int. Conf. on Concurrency Theory (CONCUR '96), LNCS 1119:34-49, Pisa (Italy), 1996

....such a divergence sensitive notion of observational congruence CCS [36] In the context of CCS and observational congruence, In recent years, CCS has been extended in different directions, among them priority and real time. Different prioritised process algebras have been developed, among them [9, 31, 11]. Investigations of observational congruence in the presence of priority have been restricted to finite, i.e. recursion free processes [31] In that approach priority is nicely reflected by the following axiom where a has a lower priority than : P a:Q = P . A variety of timed process ....

R. Cleaveland, G. Luttgen, and V. Natarjan. A Process Algebra with Distributed Priorities. In Proc. CONCUR 96, Springer LNCS 1119:34-49,1996.

....our language and derive the technical results discussed above, while Sect. 6 presents an example showing the application of our theory. Sect. 7 discusses related work, and the last section presents our conclusions and directions for future work. Due to space constraints we refer the reader to [7] for the proofs of our main theorems. 2 Motivating Example Application1 Handler2 Handler1 Site1 Site2 Network Application2 Fig. 1. Standard distributed system The example depicted in Fig. 1 motivates the need for considering a local notion of pre emption when dealing with priorities in distributed ....

R. Cleaveland, G. Luttgen, and V. Natarajan. A process algebra with distributed priorities. Technical Report TR-96-02, North Carolina State University, March 1996.

....our conclusions and directions for future work. The appendix contains characterizations of our behavioral relations as standard strong bisimulations as well as logical characterizations of these relations. Due to space constraints we omit the more straightforward proofs; these may be found in [8]. 2 Motivating Example The example depicted in Fig. 1 motivates the need for considering a local notion of pre emption when dealing with priorities in distributed systems. The system consists of two sites (computers) Site1 and Site2, that are connected via the network Network. Each site runs an ....

....the unprioritized or prioritized sort of the processes P and Q under consideration (cf. Lemma 2) By Theorem 4, we may conclude that Theta a . The other necessary inclusion is established by the following proposition. Due to space constraints its proof is omitted here and can be found in [8]. Proposition 25 The inclusion a holds. This proposition completes the establishment of the premises of Theorem 23. Thus, X = Y , i.e. Theta = Also, we have shown in Prop. 24 that = l . Hence, Theta = l , and Theorem 22 is proved. In App. A it is shown ....

R. Cleaveland, G. Luttgen, and V. Natarajan. A process algebra with distributed priorities. Technical report, North Carolina State University, Raleigh, NC, USA, 1997. To appear.

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R. Cleaveland, G. L#uttgen, and V. Natarajan. A process algebra with distributed priorities. Technical Report TR-96-02, North Carolina State University, March 1996.

....Award CCR 9257963, NSF grant CCR 9402807, and AFOSR grant F49620 95 1 0508. y Research support provided by the German Academic Exchange Service under grant D 95 09026 (Doktorandenstipendium HSP II AUFE) other aspects of system behavior, including real time [2, 3, 13, 18, 24] priorities [6, 8, 9] and probability [23] Most of this later work, however, has been devoted to modeling centralized, as opposed to distributed systems; the real time work, in particular, has (implicitly or explicitly) focused on systems with a single clock. In this paper we present a temporal process algebra, ....

R. Cleaveland, G. Luttgen, and V. Natarajan. A process algebra with distributed priorities. Technical Report TR-96-02, North Carolina State University, March 1996.

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R. Cleaveland, G. Luttgen, and V. Natarajan. A process algebra with distributed priorities. [MS96], 34--49. (p 18)

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