Camilleri, J. and Winskel, G. "CCS with Priority Choice." In Proceedings of the Sixth Annual Symposium on Logic in Computer Science, pp. 246--255. Computer Society Press, Los Alamitos, 1991.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....Priorities add a simple but powerful programming tool to CBS. Funding: From the Swedish Government agencies TFR and NUTEK, the latter supporting Chalmers membership of the Esprit Basic Research Action CONCUR2 Broadcast vs. handshake PCBS is far easier to set up than CCS with priorities [CH88, CW91] because of the difference in the communication models. Translated to a timed setting, this difference can be illustrated as follows. Consider the following classroom situation: the teacher gives the class two minutes to think about a question. The quickest student will answer, unless even this ....

Juanito Camilleri and Glynn Winskel. CCS with priority choice. In Symposium on Logic in Computer Science. IEEE, 1991.

....[10] and their utility has been demonstrated by several case studies [1, 7] Most of these case studies are based on process algebras that provide simple mechanisms for modeling nondeterminism and concurrency. Many extensions to these plain languages have been proposed, including priorities [2, 6, 8, 14]. Priorities in particular are needed to model the often used concept of interrupts, especially in hardware and communication protocols. This paper presents a case study of a real world system which shows the benefits of priorities for modeling and verifying distributed systems. Our example is ....

J. Camilleri and G. Winskel. CCS with priority choice. In Sixth Annual Symposium on Logic in Computer Science (LICS '91), pages 246--255, Amsterdam, July 1991. IEEE Computer Society Press. 130 R. Cleaveland, G. Luttgen, V. Natarajan, S. Sims

....real time. We introduce a new process algebra, called CCS dp (Calculus of Communicating Systems with dynamic priority) which essentially extends the Calculus of Communicating Systems (CCS) Milner 1989] by assigning priority values to actions. Unlike conventional process algebras with priority [Camilleri and Winskel 1995; Cleaveland and Hennessy 1990; Cleaveland et al. 1999] actions in our algebra do not have fixed or static priority values; they may change as systems evolve. It is in this sense that we refer to CCS dp as a process algebra with dynamic priority. In contrast to traditional real time process ....

Camilleri, J. and G. Winskel (1995), "CCS with Priority Choice," Information and Computation 116 , 1, 26--37.

....other automated tools) that would make it possible to parameterize the system with respect to the process algebra programming language used to build agents. Work is also underway on automated techniques for reasoning about actions with priority, probabilistic processes and real time systems (cf. [4, 10, 18, 24, 34, 49]) Acknowledgements We would like to thank Matthew Hennessy, Robin Milner and Colin Stirling for initiating and overseeing the Workbench project. We are also grateful to Lennart Beckman, Jo Blishen, Patrik Ernberg, Lars ake Fredlund, Michael Mendler, Kevin Mitchell, Fredrik Orava, Bjorn Pehrsson, ....

Camilleri, J. and Winskel, G. "CCS with Priority Choice." In Proceedings of the Sixth Annual Symposium on Logic in Computer Science, pp. 246--255. Computer Society Press, Los Alamitos, 1991.

....and an interrupt may be mutually independent actions, however they serve as control entities for different types of external events. Three central approaches to priority in process algebra are the ones by Baeten, Bergstra, and Klop [BBK86] Cleaveland and Hennessy [CH90] and Camilleri and Winskel [Cam91, CW91]. Whereas the approach in [BBK86] is not globally dynamic, Cleaveland and Hennessy do not address the issue of a general partial order structure for priorities. Camilleri and Winskel satisfy both of these features. However transitions in their model must be augmented with information about the ....

....the reader writers example. Section 5 investigates the asynchronous calculi, while related work is considered in Section 6. In particular, we discuss the relationship of PCCS to the approaches of Baeten, Bergstra, and Klop [BBK86] Cleaveland and Hennessy [CH90] and Camilleri and Winskel [Cam91, CW91]. Conclusions and plans for future work are given in Section 7. 2 Syntax of PCCS i As in SCCS, the atomic actions of PCCS i constitute an Abelian monoid (Act; Delta; 1) Actions of the form ff Delta fi represent the simultaneous, atomic execution by a process of the actions ff and fi. We will ....

[Article contains additional citation context not shown here]

J. A. Camilleri and G. Winskel. CCS with priority choice. In Proceedings of the 6th IEEE Symposium on Logic in Computer Science. IEEE Computer Society Press, July 1991.

....semaphore process. The resulting specification becomes quite complicated and cumbersome. Our specification is clear and natural, because of the explicit notion of resources in the algebra. Furthermore, since SCCS does not have priority concept, they adapted a priority operator developed for CCS [1] in the context of SCCS. On the other hand, ACSR has the built in notion of priority, which can be used to model the maximum parallel and pipeline execution of instructions. To illustrate our approach, this paper uses a hypothetical superscalar processor, called ToyP, developed by Harcourt et al. ....

J. Camilleri and G. Winskel. CCS with Priority Choice. In Proc. of IEEE Symposium on Logic in Computer Science, 1991.

....the substitution of equals for equals inside larger systems. Traditional process algebras focus on modeling the potential nondeterminism that concurrent processes may exhibit; approaches have also been suggested for introducing sensitivity to other aspects of system behavior, including priority [3, 9, 10, 13, 16, 20, 26] and concurrency [1, 8, 24] The latter work presents theories in which concurrency is treated as a primitive notion that is not reducible to nondeterminism, while the former enables the modeling of systems in which some system transitions (e.g. interrupts) may take precedence over others. In this ....

....order to extend traditional process algebras with priorities. They differ in their objectives which priority aspects of real systems or programming languages to model. The objectives arise from modeling interrupt systems [3] from programming language constructs like the PRIALT construct in occam [10, 20], and from efforts to combine real time approaches with priorities [9, 16] Another approach for extending the process algebra CCS [23] has been proposed in [13] where priorities are assigned to actions in a globally dynamic way, i.e. in one state of a system action ff may have priority over ....

J. Camilleri and G. Winskel. CCS with priority choice. In Sixth Annual Symposium on Logic in Computer Science (LICS '91), pages 246--255, Amsterdam, July 1991. IEEE Computer Society Press.

....change. Both and are congruences, and capture the intuitively desired equivalences. The changes to CBS are minimal, yet the language gains significantly in power. For example, termination at one priority level is detected by the ability to transmit at a lower level. Adding priorities to CCS [CH88, CW91] is difficult because CCS makes an autonomous action out of two controlled ones. Both these papers need very much more involved transition systems. 10. Future work Correctness of implementation. A calculus with evaluation and communication rules, ECBS, has been developed and related to CBS. ....

Juanito Camilleri and Glynn Winskel. CCS with priority choice. In Symposium on Logic in Computer Science. IEEE, 1991.

....for the Demos language compared with that of the CCS semantics. This results for the ability to construct compound atomic actions in SCCS and suggests that further more detailed studies of general simulation systems should be undertaken in formal languages with this degree of expressiveness [vGSST90, Tof90a, CW90, Tof94]. Equally it will be interesting to compare the effectiveness of other more expressive process algebras (such as [MT90, Han92] at expressing the temporal or probabilistic properties of simulations. Acknowledgements The material presented here has been under development some time and has ....

J. Camilleri, G. Winskel, CCS with priority choice. Proceedings of the sixth IEEE symposium on Logic in Computer Science, July 1990.

....synchronization occurs between two unprioritized events (e.g. a and a) the result is the unprioritized . Similarly, when a and a synchronize, the result is . This event is the only preemptive action, which gives rise to the following law: for any unprioritized a, P a:Q = P 26 In [6], Camilleri and Winskel extend CCS with a prioritized choice operator. Akin to Occam s PRI ALT, this construct selects the input event of highest priority. Also concentrating on Occam, Barrett [3] provides prioritized semantics within the context of CSP. He proceeds to show that in certain ....

J. Camilleri and G. Winskel. CCS with Priority Choice. In Proc. of IEEE Symposium on Logic in Computer Science, 1991.

....CBS with priorities. Processes that wish to speak do so at some priority. This resolves contention between utterances of differing priorities. Hearing has no priority associated with it, since what a process hears is anyway decided by the environment. Things are much harder in CCS with priorities [CH90, CW91]. Here there is only one autonomous action, a completed handshake (written ) which is silent. Priorities are associated with potential (i.e. non autonomous or controlled) actions. This leads to obvious problems. A process p can do actions a or b and prefers a, say, but what use is this if the ....

Juanito Camilleri and Glynn Winskel. CCS with priority choice. In Symposium on Logic in Computer Science. IEEE, 1991.

....B in parallel, where B begins executing one clock cycle after A (e.g. issuing instructions on consecutive cycles) This can be modeled by A Theta 1 : B: We define the binary combinator Next to denote this agent. A Next B = A Theta 1 : B Another useful operator is the priority sum operator, [CW91]. Intuitively, if in the agent A B both A and B can execute, then it is non deterministic which one is executed. We can prioritize so that if both A and B can execute, then A is preferred. Thus, A B denotes the priority sum of A and B, where A has priority over B. 3.6 Transition Graphs The ....

Juanito Camilleri and Glynn Winskel. CCS with priority choice. In LICS 91: IEEE Symposium on Logic in Computer Science, pages 246--255, 1991.

....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 ....

.... enforce it, there is no need to introduce artificial prioritized loops in the algebraic description of the system like in [14] nor to burden the algebraic description with occurrences of the priority operator like in [4] Furthermore, we observe that EMPA pt;w is different from the proposal of [13], where a prioritized choice operator 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 ....

J. Camilleri, G. Winskel, "CCS with Priority Choice", in Information and Computation 116:26-37, 1995

.... examples of process algebras are Communicating Sequential Processes (CSP) Hoa85] and The Calculus of Communicating Systems (CCS) Mil89, Mil80] although there are many variations on this theme, for instance SCCS (Synchronous CCS) Mil89] PCCS (parallel CCS) Fen96] with priority sum [CW91] with conditional operator University of Teesside, 1996 Page: Section 1.1 Integrated Formal Methods for Multi perspective Systems [Cam91] distributed [Kri91] asynchronous CSP [dBH92] Also (see section 2.2) process algebra components have featured in Hybrid Methods, e.g. LOTOS, MOSCA and ....

J. Camilleri and G. Winskel. CCS with priority choice. In Proceedings of 6th annual IEEE symposium on logic in computer science, Amsterdam, 1991. IEEE Comput. Sco. Press.

.... executing one clock cycle after A (e.g. issuing instructions on consecutive cycles) This serial operation can be modeled by A Theta (1 : B) We define the binary combinator Next to denote this process: A Next B def = A Theta (1 : B) Another useful operator is the priority sum operator, [CW91]. If in the process A B both A and B can execute, then it is non deterministic which one is executed. We can prioritize so that if both A and B can execute, then A is preferred, denoted by A B. 3 Specifying a Processor We now briefly describe the method of specifying a processor in SCCS. ....

Juanito Camilleri and Glynn Winskel. CCS with priority choice. In LICS 91: IEEE Symposium on Logic in Computer Science, pages 246--255, 1991.

....by (1) assigning each event a priority of either 0 or 1, and (2) ensuring that connected events have the same priority. In fact, the treatment of priority in CCSR can be considered an extension to the work in Cleaveland and Hennessy, whose ideas contributed to the development of our model. In Camilleri and Winskel (1991), CCS is extended with a prioritized choice operator. Akin to Occam s PRI ALT, this construct selects the input event of highest priority. In the terminology of CCSR, this notion of priority can be described by the following two restrictions: each connection set has two elements, and only one of ....

Camilleri, J., and Winskel, G. (1991), CCS with priority choice, in "Proc. of IEEE Symposium on Logic in Computer Science," IEEE Computer Society Press, Los Alamitos.

....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, ....

J. Camilleri and G. Winskel. CCS with priority choice. In Sixth Annual Symposium on Logic in Computer Science (LICS '91), pages 246--255, Amsterdam, July 1991. IEEE Computer Society Press.

....at the airport. The handshake (or rendezvous) model of communication is similar to the market model. An indication of the difficulty of respecting priorities in this model is the priority inversion problem in Ada [BA90] This model is also predominant in process calculus. The several papers [BBK85, CH88, CW91] that add priority to process calculus have all used this model, and therefore suffer from the broker s difficulties. In [CH88] an a priori semantics works out what might happen, and a second stage works out what actually happens. In [CW91] transitions are predicated on what the environment can ....

....in process calculus. The several papers [BBK85, CH88, CW91] that add priority to process calculus have all used this model, and therefore suffer from the broker s difficulties. In [CH88] an a priori semantics works out what might happen, and a second stage works out what actually happens. In [CW91], transitions are predicated on what the environment can do. This paper adds priorities to a calculus of broadcasting systems (CBS) Pra93c] The resulting CBS with priorities (PCBS) is strikingly simple, and compares very favourably with CCS with priorities. This confirms the intuition above, ....

[Article contains additional citation context not shown here]

Juanito Camilleri and Glynn Winskel. CCS with priority choice. In Symposium on Logic in Computer Science. IEEE, 1991.

....and an interrupt may be mutually independent actions, however they serve as control entities for different types of external events. Three central approaches to priority in process algebra are the ones by Baeten, Bergstra and Klop [BBK86] Cleaveland and Hennessy [CH90] and Camilleri and Winskel [Cam91, CW91]. Whereas the approach in [BBK86] is not globally dynamic, Cleaveland and Hennessy do not address the issue of a general partial order structure for priorities. Camilleri and Winskel satisfies both of these features. However transitions in their model must be augmented with information about the ....

....semantics in Section 3. The language PCCS is the subject of Section 4, while related work is considered in Section 5. In particular, we discuss the relationship of PCCS to the approaches of Baeten, Bergstra and Klop [BBK86] Cleaveland and Hennessy [CH90] and Camilleri and Winskel [Cam91, CW91]. Conclusions and plans for future work are given in Section 6. 2 Syntax of PCCS i As in SCCS, the atomic actions of PCCS i constitute an Abelian monoid (Act; Delta; 1) Actions of the form ff Delta fi represent the simultaneous, atomic execution by a process of the actions ff and fi. We will ....

[Article contains additional citation context not shown here]

J. A. Camilleri and G. Winskel. CCS with priority choice. In Proceedings of the 6th IEEE Symposium on Logic in Computer Science, Amsterdam, July 1991.

....[10] and their utility has been demonstrated by several case studies [1, 7] Most of these case studies are based on process algebras that provide simple mechanisms for modeling nondeterminism and concurrency. Many extensions to these plain languages have been proposed, including priorities [2, 6, 8, 15]. Priorities in particular are needed to model the often used concept of interrupts , e.g. in communication protocols. This paper presents a case study of a real world system which shows the benefits of priorities for modeling and verifying distributed systems. Our example is based on a case study ....

J. Camilleri and G. Winskel. CCS with priority choice. In Sixth Annual Symposium on Logic in Computer Science (LICS '91), pages 246--255, Amsterdam, July 1991. IEEE Computer Society Press.

No context found.

Camilleri, J. and Winskel, G. "CCS with Priority Choice." In Proceedings of the Sixth Annual Symposium on Logic in Computer Science, pp. 246--255. Computer Society Press, Los Alamitos, 1991.

No context found.

J. Camilleri and G. Winskel. CCS with priority choice. In Proceedings 6 th Annual Symposium on Logic in Computer Science, Amsterdam, pages 246-255. IEEE Computer Society Press, 1991.

No context found.

G. Winskel and J. Camilleri, "CCS with a priority choice," in Proceedings of LICS, 1991. [DART-124].

No context found.

J. A. Camilleri and G. Winskel, "CCS with priority choice," In Proceedings of LICS'91, 1991. To appear in Information and Computation.

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