P. Degano, R. De Nicola, and U. Montanari (1988), A Distributed Operational Semantics for CCS based on Condition/Event Systems. Acta Informatica 26, 59--91, Springer-Verlag.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....because a distinction occurs between A, in which a and b can occur simultaneously, and B in which this option is not present. Those in favor of the true concurrency approach think that the interleaving model is unrealistic and they present alternative semantic models based on Petri nets [4, 24, 17, 6, 5, 18, 23], event structures [25] or traces [10, 12] We are interested in the work on the definition of a (untimed) Petri nets semantics for PA in which it is possible to associate a Petri net representation (N [ P ] with each process term P . Several authors [6, 5, 24] have proposed a compositional ....

P. Degano, R. De Nicola, and U. Montanari. A distributed operational semantics for CCS based on Condition/Events systems. Acta Informatica, 26, 1988.

....set of basic operators which can be used to build systems from more elementary ones. 1 Recently, the two formalisms began to influence each other and to converge. More specifically, research has been conducted in finding for Process Algebra programs finite representations in terms of Petri nets [9, 10, 21, 22, 29, 11]. The main reason for such an investigation is that Petri net representations explicitly model parallelism and can in this way be understood as a concurrent semantics for Process Algebras. In this work, we suggest that such a representation implies other significant benefits as well. We propose ....

....components correspond to places of Petri nets. Consequently, net transitions are now of the form fC 1 ; C n g u fC n 1 ; C n m g where fC 1 ; C n m g are sequential components and u is an action of the agent. The decomposition idea was first proposed in [9] and also used in [10], 21] 22] 29]and [11] In the following, the details of the decomposition are presented and subsequently the transition relation of the Petri net is defined by induction on the syntactic structure of sequential components. Our presentation follows the ideas of [11] 3.1 The Decomposition In ....

P. Degano, R. DeNicola and U. Montanari, A Distributed operational semantics for CCS based on condition/event systems, Acta Informatica 26 (1988) 59-91.

....of CCS [Mil89] reduces parallelism to non determinism (or interleaved execution of actions: the expansion theorem for CCS) This is due to the presence of only one observer with the power to observe one action at a time. There are other approaches which describe a non interleaving semantics [Pra86, DDM88, CH89, KHCB91a] but do so only at a logical level. In this paper we provide a semantics for CCS which takes into account physical available distribution . Given that there is no uniformity in the nature of distributed architecture, one needs to define distributed . For that we consider the natural language ....

....to [KHCB91b] A detailed comparison between [KHCB91b] and [CH89] is presented in [KHCB91b] In short, both the approaches consider spatial issues in distributed computation at the logical level. They do not consider limitations imposed by a physical architecture. In distributed semantics such as [DDM88] the primary concern is causality and not physically distributed computing elements. 3.1 Examples As the syntax for distributed CCS is different from CCS we present a few examples which illustrate modelling certain aspects of distributed systems. Example: The following is an encoding of RPC ....

P. Degano, R. DeNicola, and U. Montanari. A Distributed Operational Semantics for CCS Based on Condition/Event Systems. Acta Informatica, 26:59--91, 1988.

....The proof for this is similar to the proof for the correctness of the pure CCS translation and easily follows from structural induction in the syntactic representation of P. 2 The above illustrates a methodology for extending the SOS style to the true concurrent case first proposed in [13]: identify the sequential components and define a SOS style transition relation for these. The structure of states then has a parallel operation (here Phi) which gives the structure of a Petri Net. It is easily seen that the operation Phi forms a free monoid where ; is the identity; thus, the ....

....for these. The structure of states then has a parallel operation (here Phi) which gives the structure of a Petri Net. It is easily seen that the operation Phi forms a free monoid where ; is the identity; thus, the structure is isomorphic to a Place Transition Net [22, 29] Previous works, e.g. [13], have used Petri Nets as the domain for giving true concurrent semantics to other languages. 18 The Petri Net defined by Net [ Linda] provides a true concurrent semantics for our Linda calculus, where the computation of the match predicate is inherent in the structure of these nets. That is, ....

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Pierpaolo Degano, Rocco DeNicola, and Ugo Montanari. A distributed operational semantics for CCS based on Condition/Event systems. Acta Informatica, pages 59--91, 1988.

....about the syntactical structure of terms is encoded within places so that the relationships among sequential terms are smoothly preserved. This is exploited to define net transitions by means of inductive rules similar to those for the interleaving semantics for the process algebra, as shown in [8, 12]. In the label oriented approach, instead, each net place corresponds to a sequential subterm independently of its position w.r.t. static operators. As a consequence, instances of the same sequential term occurring in different positions w.r.t. static operators can be represented by multiple ....

....I[ System] Theorem 4.8 Let B = f(E; Q) 2 G 0 Theta M(V) j Q = dec(E)g. Then B is a strong bisimulation. Proof See Appendix A. 5 Properties of the Proposed Semantics In this section we discuss the compactness of the generated nets w.r.t. those generated by the location oriented approach of [8, 12] and the compactness of the underlying reachability graphs w.r.t. the LTSs of the corresponding algebraic terms. Moreover, we discuss the finiteness of the nets and we investigate the reinterpretation at the process algebraic level of structural information computed at the net level. ....

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P. Degano, R. De Nicola, U. Montanari, "A Distributed Operational Semantics for CCS Based on Condition /Event Systems", in Acta Informatica 26:59-91, 1988

....of the system: problems related to concurrency and communication, peculiarities due to the kind of communication, whether it is synchronous or asynchronous, sequential execution of tasks and also the particular goals of individual agents. In the classical approaches to concurrent programming [34, 28, 53, 48, 42, 33, 44], all these issues are addressed simultaneously and treated at the same level, without making any explicit distinction between problems related to communication and computation problems. At present, in fact, many concurrent applications use a set of ad hoc patterns for the coordination of the ....

P. Degano, R. DeNicola, and U. Montanari. A distributed operational semantics for CCS based on condition/event systems. Acta Informatica, 26, 1988.

....of process algebraic terms into Petri nets. The aim of such an approach is to provide the algebraic theory via a Petri net semantics with a partial order semantics. The most well known example of this approach is the Petri Box Calculus of [15, 16] Other examples of this line of research are [19, 21, 29, 30, 45, 49, 59]. In this chapter, the converse approach is pursued. In particular, in Section 6.3, a translation from labeled P T nets into algebraic terms is given. Other examples of this approach are [20, 22] The main difference between the approach taken in this chapter and other approaches is that this ....

P. Degano, R. De Nicola, and U. Montanari. A Distributed Operational Semantics for CCS Based on Condition /Event Systems. Acta Informatica, 26(1/2):59--91, October 1988.

....nets. Related work. One way to integrate P T nets with process algebra is to give a net semantics for terms in the algebra, thus providing the process algebra with a true concurrency semantics. Examples of this approach are Best, Devillers, and Hall [10] Degano, De Nicola, and Montanari [13], Van Glabbeek and Vaandrager [16] Goltz [19] Montanari and Yankelevich [28] Olderog [29] and Taubner [33] As explained, this paper does the converse. It gives an algebraic semantics for P T nets. Examples of this approach are Baeten and Bergstra [2] Boudol, Roucairol, and De Simone [11] ....

P. Degano, R. De Nicola, and U. Montanari. A Distributed Operational Semantics for CCS Based on Condition /Event Systems. Acta Informatica, 26(1/2):59--91, October 1988.

....execute faster than the second one, it asserts that the first process is faster than the second one. There have indeed been several process calculi for distributed systems. They are extensions of existing process calculi with some features of distributed computing: causality between events (e.g. [6]) location information (e.g. 4] port passing mechanism (e.g. 8, 11] and local time (e.g. 17] but none addresses the issue of communication delay. Also, there have been several temporal extensions of process calculi for synchronous communication, for example [7, 13, 14, 16, 20, 22] ....

Degano, P, deNicola, R. D., and Montanari, U., A Distributed Operational Semantics for CCS Based on Condition / Event Systems, Acta Informatica, Vol.26, p5991, 1988. 9 To define this, we need to extend the semantics of the calculus; but we leave the details of the extensions to [19].

....denoted by an exclamation mark: if P is a process, then P stands for a countably infinite number of concurrent copies of P . It is shown in [13] that this subset suffices to simulate important aspects of the calculus. Petri net semantics of process algebras has been studied in, e.g. [1, 6, 10, 17, 18, 21]. In such a semantics, a Petri net is associated with each process; the idea is that this Petri net expresses the concurrency present in the process in a more direct way than the interleaving transition system. Here we wish to stress that a Petri net (and in particular a P T net) is just a ....

....may be viewed as a one stroke implementation of its heating rules. The semantic mapping associates a multiset S in M with each process term P . Intuitively, S is the decomposition of P into its concurrent subprocesses. Thus, the semantic mapping is similar to the decomposition mappings of [6, 18]; however, as opposed to [6, 18] it also decomposes all (guarded) subterms of P . Another difference is that it decomposes into multisets rather than sets; in fact, the replication operation forces us to consider non safe Petri nets. The advantages of non safe nets have been pointed out in [10] ....

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P.Degano, R.De Nicola, U.Montanari; A distributed operational semantics for CCS based on Condition/Event systems, Acta Informatica 26 (1988), 59-91

....of hierarchical nets. Related work. One way to integrate P T nets with CCS like calculi is to give a net semantics for terms in the calculus, thus providing the calculus with a true concurrency semantics. Examples of this approach are Best, Devillers, and Hall [8] Degano,De Nicola, and Montanari [11], Van GlabbeekandVaandrager [15] Goltz [16] Montanariand Yankelevich [24] Olderog [25] and Taubner [28] As explained, this paper does the converse. It gives an algebraic semantics for P T nets. Examples of this approach are Baeten and Bergstra [2] Boudol, Roucairol, and De Simone [9] and ....

P. Degano, R. De Nicola, and U. Montanari. A Distributed Operational Semantics for CCS Based on Condition/Event Systems. Acta Informatica, 26(1/2):59--91, October 1988.

....E. These three semantics are at the base of the integrated approach for modelling and analysing concurrent systems described in (Bernardo et al. 1994a) The net semantics LocON [ E] has been defined by resorting to a suitable extension of the structured operational semantics approach for nets (Degano et al. 1988; Olderog, 1991) which consists of associating with each term E a place transition net such that: places correspond to the sequential subterms of E and its derivatives, transitions are defined by induction on the syntactical structure of the sets of sequential subterms, and markings correspond ....

....by its net semantics. The main drawback of such a net semantics is that it usually associates huge nets with EMPA terms. This is a drawback shared by all the net semantics exploiting the syntactical structure of the terms (notably, the parallel composition operator) to define the set of places (Degano et al. 1988). These are sometimes called location oriented net semantics. However, there is another approach, called label oriented, which partly ignores the syntactical structure of terms and is based mainly on information about transition labels (Goltz, 1988; Gorrieri Montanari, 1995) While the former ....

Degano, P., De Nicola, R., & Montanari, U. 1988. A Distributed Operational Semantics for CCS Based on Condition/Event Systems. Pages 59--91 of: Acta Informatica, vol. 26.

....[Pet73, Rei85] are a widely used model of concurrency. This model is attractive from a theoretical point of view because of its simplicity and because of its intrinsically concurrent nature, and has often been used as a semantic basis on which to interpret concurrent languages (see for example [Win82, Old87, vGV87, DDM88]) For Place Transition (PT) nets, having a satisfactory semantics one that does justice to their truly concurrent nature, yet is abstract enough remains in our view an unresolved problem. Certainly, many different semantics have been proposed in the literature; we briefly discuss some of them ....

P. Degano, R. De Nicola, and U. Montanari. A Distributed Operational Semantics for CCS based on Condition/Event Systems. Acta Informatica, n. 26, pp. 59--91, 1988.

....notion of behavior is an ascending path in the A cube. Natural, that is, for events that happen sequentially. In the true concurrency hierarchy, a path or trace going up one event at a time is called interleaving semantics, while one going up several events at a time is called step semantics [DDNM88] (this term motivated by Petri net terminology [Rei85, p.20] and the form of concurrency implicit in SCCS [Mil83] both being weaker [GG89] than partial order semantics [Gre75, Gra81, Pra82] According to [Pra91, GJ92] a truly concurrent trajectory is a homotopy class of paths, meaning a broad ....

P. Degano, R. De Nicola, and U. Montanari. A distributed operational semantics for CCS based on condition/event systems. Acta Informatica, 26(1/2):59--91, October 1988.

....system. In general, such conditions are global, since the premises of a rule may impose arbitrary assumptions on the behaviour of the sub components of the state under analysis. This is the way the original, interleaving operational semantics for ccs was presented [60] Suitable extensions such as [25] have been then used for giving an account of truly concurrent semantics for process algebras. The solution exemplified by G erard Berry and G erard Boudol with their chemical abstract machine (shortly, cham) 6] is loosely based on the firing steps 8 A typical example is the span categories by ....

P. Degano, R. De Nicola, and U. Montanari. A distributed operational semantics for ccs based on condition/event systems. Acta Informatica, 26:59--91, 1988.

....two causally independent events. There are many different ways to provide a truly concurrent operational semantics for process algebras: i) mapping to Petri nets or event structures by induction on the syntax of the agents [Win82, GM84] ii) or on the structure of the proofs of transitions 22 [Old87, DDM88, GM94]; iii) defining the concurrent computations by assigning a residue structure to the CCS transition system [BC91] and iv) defining the concurrent computations by direct axiomatization [FM90] However, all the proposed approaches are essentially equivalent (see e.g. GM94] in the sense that they ....

P. Degano, R. De Nicola, U. Montanari, A Distributed Operational Semantics For CCS Based On Condition/Event Systems, Acta Informatica 26, 1988, pp. 59-91.

.... to write modular and expressive programs, and to model systems equipped with synchronization primitives (to achieve modularity in de ning the net associated to the synchronous composition of two programs, the translations presented in the literature involve complex, and often ad hoc, constructions [48,26,36,20,28,7]) Besides transitions and ordinary places (here called stable places) zs nets include a distinguished set of zero places for modeling idealized resources that remain invisible to external observers, whilst stable markings, which just consist of tokens in stable places, de ne the observable ....

P. Degano, R. De Nicola, and U. Montanari. A distributed operational semantics for CCS based on condition/event systems. Acta Inform., 26(1-2):59-91, 1988.

....Comunicazione; by Esprit Working Groups CONFER2 and COORDINA; and by MURST project Tecniche Formali per Sistemi Software. this model offers a basic concurrent framework that has often been used as a semantic foundation for system analysis and for the interpretation of many concurrent languages [30, 14, 24, 11, 16, 3]. However, though net transitions allow for token synchronization, the basic net model does not offer any synchronization mechanism among transitions, while this feature is essential to write modular and expressive programs, and to model systems equipped with synchronization primitives. In fact, ....

P. Degano, R. De Nicola, and U. Montanari, A distributed operational semantics for CCS based on condition/event systems, Acta Informatica 26(1-2), 59--91 (1988).

....considered as one of the most attractive models of concurrency. As a matter of fact, this model offers a basic concurrent framework that has often been used as a semantic foundation on which to interpret many concurrent languages (Winskel 1982; Van Glabbeek and Vaandrager 1987; Olderog 1987; Degano et al. 1988; Gorrieri and Montanari 1995; Best et al. 1992) However, though net transitions allow for token synchronization, the basic net model does not offer any synchronization mechanism among transitions, while this feature is essential to write modular and expressive programs. In fact, all the above ....

Degano, P., De Nicola, R., and Montanari, U. (1988), A Distributed Operational Semantics for CCS based on Condition/Event Systems, Acta Informatica 26, 59--91.

....1 Introduction Petri nets [18,17] are unanimously considered one of the most attractive models of concurrency. As a matter of fact, this model ooeers a basic concurrent framework that has often been used as a semantic foundation on which to interpret concurrent languages (see for instance [19,10,16,5,8,2]) However the basic net model does not ooeer any synchronization mechanism among transitions, while this feature is essential to write modular, expressive programs. Thus all the above translations involve complex constructions for the net de ning the synchronized composition of two programs. In ....

P. Degano, R. De Nicola, and U. Montanari. A Distributed Operational Semantics for CCS based on Condition/Event Systems. Acta Informatica, 26:5991, 1988.

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P. Degano, R. De Nicola, and U. Montanari (1988), A Distributed Operational Semantics for CCS based on Condition/Event Systems. Acta Informatica 26, 59--91, Springer-Verlag.

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P. Degano, R. De Nicola, and U. Montanari. A distributed operational semantics for CCS based on condition/event systems. Acta Informatica, 26, 59--91, 1988.

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P. Degano, R. De Nicola, and U. Montanari. A distributed operational semantics for CCS based on condition/event systems. Acta Informatica, 26, 59--91, 1988. (pp 7, 28)

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P. Degano, R. De Nicola, and U. Montanari (1988), A Distributed Operational Semantics for CCS based on Condition/Event Systems. Acta Informatica 26, 59--91, Springer-Verlag.

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P. Degano, R. De Nicola & U. Montanari, A Distributed Operational Semantics for CCS Based on Condition/Event Systems, Acta Informatica 26, pp. 59-91, 1988.

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