R. d. Simone, Higher-level synchronising devices in Meije--SCCS, Theoretical Comput. Sci., 37 (1985), pp. 245--267.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....network, client server protocol, chessboard grid) the theoretical and practical merits of our operator. 1 Introduction Process algebras have been designed as a theoretical framework for the study of concurrency. Classical examples of process algebras are: ACP [1] CCS [24, 25] CSP [15] MEIJE [7], etc. There also exist specification languages, which combine process algebraic concepts with features borrowed from (functional or imperative) programming languages. For example, the Occam [4] language based on CSP, the Crl [12] language based on ACP, and the Lotos [16] language which combines ....

Robert de Simone. Higher-level synchronising devices in Meije--SCCS. Theoretical Computer Science, 37:245--267, 1985.

....equivalence. For example, a process that simply performs an action a and then stops ought to be the same as one that has several different ways of doing a s and then stopping, since one a or stopped process is the same as another. A wide variety of notions of equivalence have been proposed, e.g.[28,31,20,5,21,27,41], appropriate for different kinds of process algebras and conceptual settings. Process equivalences can be partially ordered by fineness: finer notions make more distinctions between processes; coarser ones consider more processes identical. Both fine and coarse notions are useful in theory and ....

R. de Simone. Higher-level synchronising devices in meije-SCCS. Theoretical Computer Sci., 37(3):245--267, 1985.

....intended for the theoretical study of concurrency, process algebras can also be used for the formal description of communication protocols and distributed systems. The word process algebras encompasses pure mathematical calculi (e.g. Acp [BK84] Ccs [Mil80, Mil89] Csp [Hoa85, BHR84] Sccs [dS85] as well as more elaborate languages (such as Fdr [For97] Lotos [ISO88b, BB88] Crl [GP95] Occam [Cam89] which provide additional features intended for the description of real systems (e.g. user defined data types and modules) Semantically speaking, process algebras have strong ....

Robert de Simone. Higher-level synchronising devices in Meije--SCCS. Theoretical Computer Science, 37:245--267, 1985.

....2 The expression replacing the j operator is strikingly different from our three examples at the start because of the condition it poses on the action set. As it happens, this way of showing derivability is often used; Mil83] uses it to show the derivability of the fl conjunction operator, and [dS85] uses it as the basis of his proof that any new operator whose operational semantics is given by structured inference rules is derivable from MEIJE SCCS. A third, and this time apparently different, notion of derivability is used by [Mil83] To prove that morphism is derivable, we note that for ....

....thus ensuring that the right hand side has an exactly similar derivation. Further, the resulting states on both sides continue to have the same form, and so lead back into the bisimulation. 5. 3 Some derivability and non derivability results Before we begin on our results, we quote a result from [dS85], which says that SCCS augmented with the Delta operator gives a complete calculus from which any operator defined by structured inference rules can be derived, using a technique rather like our proof of the derivability of j . The Delta operator is defined by the rules Persistent Delay E ....

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R. de Simone. Higher level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, 37(3):245--268, 1985. 142 K. V. S. Prasad

....at the format of such transition rules to know that the contexts of the language are faithful. We show that this is indeed the case for the rules in unary De Simone format over Sigma, which we will often just call De Simone format. It is a simplied version of the format introduced by De Simone [DS85] (the main restriction is that only one action at a time is observable) In rule (3) below, X r , 1 r n, and Y j , j 2 J , are metavariables which are instantiated with processes when the rule is applied. Denition 2.18 (unary De Simone format) A transition rule X j j Gamma Y j (j 2 J) f(X ....

R. De Simone. Higher level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, 37:245267, 1985.

....2 The expression replacing the j operator is strikingly different from our three examples at the start because of the condition it poses on the action set. As it happens, this way of showing derivability is often used; Mil83] uses it to show the derivability of the fl conjunction operator, and [dS85] uses it as the basis of his proof that any new operator whose operational semantics is given by structured inference rules is derivable from MEIJE SCCS. A third, and this time apparently different, notion of derivability is used by [Mil83] To prove that morphism is derivable, we note that for ....

....thus ensuring that the right hand side has an exactly similar derivation. Further, the resulting states on both sides continue to have the same form, and so lead back into the bisimulation. 5. 3 Some derivability and non derivability results Before we begin on our results, we quote a result from [dS85], which says that SCCS augmented with the Delta operator gives a complete calculus from which any operator defined by structured inference rules can be derived, using a technique rather like our proof of the derivability of j . The Delta operator is defined by the rules Persistent Delay E ....

[Article contains additional citation context not shown here]

R. de Simone. Higher level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, 37(3):245--268, 1985. 148 K. V. S. Prasad

....at the format of such transition rules to know that the contexts of the language are faithful. We show that this is indeed the case for the rules in unary De Simone format over Sigma, which we will often just call De Simone format. It is a simplified version of the format introduced by De Simone [DS85] (the main restriction is that only one action at a time is observable) In rule (3) below, X r , 1 r n, and Y j , j 2 J , are metavariables which are instantiated with processes when the rule is applied. Definition 2.20 (unary De Simone format) A transition rule X j j Gamma Y j (j 2 J) ....

R. De Simone. Higher level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, 37:245--267, 1985.

....of higher order bisimulation (perhaps one based on the use of location, as mentioned in Section 4.2) coincide. Expressiveness of calculus Our study on the translation of HO and calculus into calculus may be seen as just an aspect of a more general question: how expressive is the calculus In [DS85], Robert de Simone has proved that Meije [AB84] and SCCS [Mil83] are complete expressive in the sense that any operator which can be defined by rules which obey certain natural conditions can also be defined directly in terms of the basic combinators of either calculus. How far here can we go with ....

R. De Simone. Higher level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, 37:245--267, 1985. Bibliography 190

....if it can do only one action at a time; concrete refers to the absence of internal actions or internal choice. 1 to avoid repetitive (pre)congruence proofs, and to explore the limits of sensible TSS de nitions. A rst congruence format for bisimulation equivalence was put forward by de Simone [26], which was extended to the GSOS format by Bloom, Istrail Meyer [7] and to the tyft tyxt format by Groote Vaandrager [19] The latter format was supplied with a well foundedness criterion, which was subsequently eliminated [13] The tyft tyxt format was extended with negative premises [8, ....

R. de Simone (1985): Higher-level synchronising devices in Meije-SCCS. Theoretical Computer Science 37, pp. 245-267.

.... x : z(x) x : ax=z] x : ax and z( x : z(x) x : ax=z] a x : ax. 2.3 Transition system speci cations In this subsection, we generalize the notion of TSS from conventional terms to binding terms. The meaning of TSSs is discussed in Section 3. The TSSs of [20] which originate from [29], de ne binary transition relations by means of transition rules with positive premises. An extension to transition rules with positive and negative premises was presented in [18, 7] and a further extension to the speci cation of unary and binary relations was presented in [31] In all three ....

....B. 18 Bisimulation is a frequently used equivalence to abstract from irrelevant details of operational semantics. Originally introduced in modal logic, it was introduced in process theory in [26] The rst format guaranteeing that bisimulation is a congruence appears to be the de Simone format [29]. The original panth format generalizes the ntyft ntyxt format of [18] for unary predicates, which in turn extends the tyft tyxt format of [20] with negative premises. The original panth format also generalizes the path format of [6] which extends tyft tyxt format as well. 4.1 Bisimulation In ....

R. de Simone. Higher-level synchronising devices in MEIJE{SCCS. Theoretical Computer Science, 37:245-267, 1985.

....de nitions are not, however, inductive on term structure we have not constructed an SOS from a set of reduction rules. Several authors taken labelled transitions as primary, considering calculi equipped with labelled transitions de ned by an SOS in some well behaved format; c.f. among others [3,6,8,13,18,23,41]. The relationship between the two is unclear 30 one would like conditions on rewrite rules that ensure the labelled transitions of Section 4 are de nable by a functorial operational semantics [41] Conversely, one would like conditions on an SOS ensuring that it is characterised by a ....

R. de Simone. Higher-level synchronising devices in meije{SCCS. Theoretical Computer Science, 37:245-267, 1985.

....proof will be given in an extended version of this paper. 5 Translation into the Meije Process Calculus The cooperation semantics is not really constructive, in the sense that it does not tell how to execute programs. We now give an implementation of Pure CRP into Boudol s process calculus Meije [6,8]. We choose this calculus because it is able to handle together synchrony and asynchrony, which is not possible in less powerful calculi such as CCS. In addition to an implementation of CRP in a classical process calculus, the Meije translation provides us with an automatic program verification ....

....Esterel system. Since the semantical aspects of synchrony and asynchrony are kept independent, other asynchronous communication policies between synchronous nodes could be studied in the same way. They could also be translated into Meije since this calculus is universal among process calculi [8]. The CRP paradigm relies on a careful separation between the synchronous and asynchronous layers. Deeper unifications of synchrony and asynchrony should be investigated. For the time being, we have no idea of which programming concepts could be appropriate for that purpose. ....

R. de Simone. Higher-level synchronising devices in Meije-SCCS. Theoretical Computer Science, 37:347--360, 1985.

....if it can do only one action at a time; concrete refers to the absence of internal actions or internal choice. to avoid repetitive (pre)congruence proofs, and to explore the limits of sensible TSS definitions. A first congruence format for bisimulation equivalence was put forward by de Simone [26], which was extended to the GSOS format by Bloom, Istrail Meyer [7] and to the tyft tyxt format by Groote Vaandrager [19] The latter format was supplied with a well foundedness criterion, which was subsequently eliminated [13] The tyft tyxt format was extended with negative premises [8, ....

R. de Simone (1985): Higher-level synchronising devices in Meije-SCCS. Theoretical Computer Science 37, pp. 245--267.

....calculus so to ensure location invariance during migration. One of the advantages of SOS semantics is that it helps in developing an algebraic theory of the language, based on the concept of bisimulation. This task is particularly facilitated when the rules are in the so called De Simone format [9, 11], or similar formats [4] since such formats ensures that bisimulation is a congruence. In our case the labels of the transitions contain agents and therefore we need to consider a sort of higher order extension of the De Simone format along the lines of [2] In the future we intend to check ....

R. de Simone. Higher-level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, 37(3):245--267, 1985.

....by applying bisimilarity laws that do not belong to structural congruence) Another interesting direction could be to adapt our methods to open terms, in order to be able to prove not only bisimilarity results, but also general bisimilarity laws. To this aim, relevant works include [Ren97] and [Sim85]. Finally, the proofs of this paper could be mechanised reusing the work of [Hir97] which could allow one, using reAEection [Bou97] to extract a certied bisimilarity checker. It seems sensible to think, however, that some more work has to be done in order to make these proofs tractable for the ....

R. De Simone. Higher-level synchronising devices in Meije-SCCS. Theoretical Computer Science, (37):245267, 1985.

....semantics are to a large extent language independent: many important properties of SOS style de nitions follow from the syntactic form of the inference rules, and can be established for whole classes of languages ( formats ) at the same time. Examples of contributions along these lines are [1, 4, 7, 10, 14, 16, 21, 24]. The resulting theory allows one to develop a simple process algebra for concurrency with substantial mathematical support. For example, one may build a process algebra in the general style of CCS, giving operations their behavior by rules in a standard format. The SOS theory will allow one to ....

R. d. Simone. Higher-level synchronising devices in meije{SCCS. Theoretical Comput. Sci., 37:245-267, 1985.

....are definable. We also determine that some operators related to nondeterminism and sequential composition are not definable. Related work includes Milner s investigation [13] of the definable behaviours in a language containing only prefixing and choice operators, and de Simone s investigation [5] of the definable operators in the synchronous process algebras MEIJE and SCCS. One main difference between the present work and de Simone s is that de Simone considers a synchronous form of composition as a primitive operator. This operator forces its arguments to execute in lock step, as if ....

....operators is called a de Simone set if the transitions on terms in T op;M are exactly the transitions which can be proven from a set of de Simone rules. An operator is a de Simone operator if it is in a de Simone set. 2 16 The class of de Simone operators was first suggested by Robert de Simone [5] who proved that these operators are exactly the definable operators in the synchronous algebras MEIJE and SCCS. We use the same definition, only slightly adapted to our framework. Practically all operators studied in process algebras are de Simone operators (in two recent papers [6, 3] more ....

R. de Simone. Higher-level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, 37(3):245--267, 1985.

....interpretation of closed terms into transition systems, with actions as transition labels. Operators and non closed expressions are then interpreted as transition system transformers; this semantics is defined through behaviour rules in a structural operational style, with a particular format (see [dSi85], VG88] We shall describe our format for rules in section 2.4. Special operators are action renamings and recursive definitions. They are present in all process calculi. 2.1 Actions In all process algebras actions are themselves structured. This structure is what allows for synchronization ....

....have been made both for the Meije0 calculus and for BasicLotos (the prototype has been presented in [MV89] The Meije0 operators are correctly classified by our definitions: the prototype accepts stricty more Meije0 programs than the preceeding Auto system. Some other Meije Sccs operators (see [dSi85]) can be added easily to this syntax, including ticking, 13 operator parameters scan algorithm sequence ( action : p; sieve ) action = sieve (action) if action then state = check(p; sieve ) add transition(action, state) sum (p q; sieve ) scan(p; sieve ) scan(q; sieve ) Sccs ....

R. De Simone, "Higher-Level Synchronising Devices in Meije-Sccs", Theoretical Computer Science 37, p245-267, 1985

....prove bisimilarity results between in nite states processes. On the contrary, the idea is rather to use the automation of the up to techniques to verify a proof on paper, once we know that the up to techniques apply. Following this approach, work is in progress to adapt our methods to open terms [10,12], in order to be able to prove not only bisimilarity results, but also general bisimilarity laws (like for example the replication theorems) Another interesting direction could be the mechanisation of the proofs of this paper, reusing the work of [5] which could allow one to extract a certi ed ....

R. De Simone. Higher-level synchronising devices in Meije-SCCS. Theoretical Computer Science, (37):245267, 1985.

....Alan Jeffrey has shown that CSP and SCCS can be translated into each other [J92] Our translation is similar in spirit to his translation of CSP into SCCS; a technical difference being that Jeffrey expresses infinite choice in SCCS via unguarded recursion, whereas we use infinite summation. In [Si85] Robert de Simone has proved that any process calculus whose operational semantics is given in a certain format, is derivable in SCCS. His result is valid for 14 U. HOLMER calculi with finite action sets. It is not yet clear to the author to what extent it applies to CBS, but one might suspect ....

de Simone, R. Higher-level synchronising devices in Meije-SCCS, Theoretical Computer Science, Vol 37, pp. 245-267. North-Holland, 1985. INTERPRETING BROADCAST COMMUNICATION IN SCCS 15

....Abr89] He and Ong then proved that this model is sound but not complete [Abr87, Ong88, AO93] The internal choice operator in Section 12 is inspired by an operator introduced by De Nicola and Hennessy [DH87] in a CCS like process calculus. Studies of format of operators in concurrency include [DS85, BIM88, ABV94, GV92] and in functional languages [Blo90, How96, San97a] The L#vy Longo Trees were introduced by Longo [Lon83] where they were simply called trees developing an original idea by Levy [L#v76] They were called L#vy Longo Trees by Ong [Ong88] B#hm Trees are studied in depth in ....

R. De Simone. Higher level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, 37:245267, 1985.

....tyft tyxt definition. 1.1 Related Work In order to simplify the specification of concurrent languages, extensive work has been done in metatheories for SOS definitions of process algebras, especially with regard to the congruence property for bisimulation. Rule formats such as de Simone s format [dS85], the tyft tyxt by Groote and Vaandrager [GV92] and the GSOS rule format by Bloom, Istrael and Meyer [BIM95] guarantee that bisimulation is a congruence. Extensions of these rule formats for including negative premises and predicates have made the rule formats of greater practical use [Gro93, ....

Robert de Simone. Higher-level synchronising devices in Meije-SCCS. Theoretical Computer Science, 37:245--267, 1985.

....as a mechanism to give operational meaning to classes of process languages. Main ingredients of such a semantics are SOS rules, which describe how the behaviour of a composite process depends on the behaviour of its component processes. Many general formats for SOS rules have been proposed (e.g. [dS85, BIM88, GV90, Gro90]) and a number of important results for process languages defined in these formats have been established. For example, various behavioural equivalences on processes were shown to be preserved by all process operators definable in these formats [dS85, BIM88, GV90, Gro90, Vaa91, Uli92, vG93, Blo93] ....

....have been proposed (e.g. dS85, BIM88, GV90, Gro90] and a number of important results for process languages defined in these formats have been established. For example, various behavioural equivalences on processes were shown to be preserved by all process operators definable in these formats [dS85, BIM88, GV90, Gro90, Vaa91, Uli92, vG93, Blo93] and (completed) trace congruences with respect to these formats where discovered [BIM88, GV90, Gro90, Vaa91, Uli92, vG93] In [ABV92, Ace94] Aceto, Bloom and Vaandrager showed how axiomatic characterisations can be derived for equivalences on processes. More recently, SOS was used as a ....

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R. de Simone. Higher-level synchronising devices in MEIJE-SCCS. Theoretical Computer Science, Vol. 37, pp. 245--267, 1985.

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R. d. Simone, Higher-level synchronising devices in Meije--SCCS, Theoretical Comput. Sci., 37 (1985), pp. 245--267.

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Robert de Simone. Higher-level synchronising devices in Meije--SCCS. Theoretical Computer Science, 37:245--267, 1985.

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