Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Proc. of Euro-Par'97, LNCS 1300, pages 554--561. SpringerVerlag, 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....has an input polar and an output polar , which in turn can be considered as the input port from, and the output port to, the channel . The main difference from [Amadio96] and [Odersky95] is that in the calculus, only output polars can be transmitted through a communication channel. Ravara97, Merro00] and others have adopted a similar restriction, but in the calculus this restriction is enforced syntactically. As a consequence, only output polar substitution can be caused by input prefix, while in [Odersky95] substitution may involve names with both polarities and in [Amadio96] it ....

....can be caused by input prefix, while in [Odersky95] substitution may involve names with both polarities and in [Amadio96] it may affect both input and output usage of a name. One of the advantages in using polars to enforce this restriction rather than using the implicit restriction as in [Ravara97] and [Merro00] is the simplification afforded in describing and proving some properties of bisimulations, such as bisimilarity between being preserved by m.tvuxw y r m.tvuxw y s for all input prefixes m.tvuxw . The notion of polarised ports exists in many forms of communication. For ....

Ant onio Ravara andVascoT. Vasconcelos. (1997). Behavioural types for a calculus of concurrent objects. In C. Lengauer, M. Griebl, and S. Gorlatch, editors, Proc. of Euro-Par'97, LNCS 1300, pages 554--561. Springer-Verlag.

....the sense that it always terminates and its answer is equivalent to the typability problem. 5 Related work and conclusion Many di erent studies are currently related to the static analysis of non uniform service availability. Following lines proposed by Nierstarz [Nie93] Ravara and Vasconcelos [RV97] on one hand and Najm and Nimour [NN97] on the other hand, advocate the use of more sophisticated type abstractions (in fact, the structure of their types is a process calculus) Their work is very promising as their abstractions preserve more causal relations. However, the feasibility of type ....

Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Euro-Par'97, LNCS 1300. Springer-Verlag, 1997.

....the sense that it always terminates and its answer is equivalent to the typability problem. 5 Related work and conclusion Many different studies are currently related to the static analysis of non uniform service availability. Following lines proposed by Nierstarz [Nie93] Ravara and Vasconcelos [RV97] on one hand, and Najm and Nimour [NN97] on the other hand, advocate the use of more sophisticated type abstraction (in fact, the structure of their types is a process calculus) Their work is very promising as their abstractions preserve more causal relations. However, the feasibility of type ....

Ant'onio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Euro-Par'97, LNCS 1300. Springer-Verlag, 1997. 15

....semantic characterization) we concentrate on the static detection of safety orphans. Type systems for concurrent objects and actors, with uniform or non uniform behaviors, have been the subject of active research in the last years ( VAS 93] NIE 95] KOB 94] KOB 95] PUN 96] NAJ 97] RAV 97] FOU 97] DAL 97] and their more recent works) Two opposite approaches have been followed: explicit and implicit typing. Explicit types may provide more precise information but are sometimes very hard to write for the programmer (they might be much more complex than the program itself) We ....

....our knowledge, it requires that actors have an infinite life time and that they always accept the same set of messages, which are precisely the two requirements that we wish to reject as they constrain actors to behave as usual objects and reject the non uniform behaviors. Ravara introduced in [RAV 97] the notion of persistent bad redex which correspond to our orphan messages (both safety and liveness) However, to our knowledge, his semantics does not explicitely compute errors as we proposed in this part. The purpose of the following type systems is to detect ML ACT expressions that may ....

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RAVARA A., VASCONCELOS V. T., "Behavioural Types for a Calculus of Concurrent Objects", Proc. of EuroPar'97, LNCS 1300, Springer-Verlag, 1997.

....been studied, the focus was, for now, on the semantics front. 7 Other approaches to the speci cation of reactive and concurrent systems have also been explored, namely temporal logic [CRSS98, DRCS97, ECSD98, SSC98] the situation calculus [Ram97] observational logic [Res97] and type theory [RV97a, RV97b] Abductive reasoning within temporal logic has been studied in the submitted PhD thesis [Gou98] 3.7 LaMI: Evry, France Our approach to the feature interaction problem is to use axiomatic speci cation formalisms in order to clearly identify interactions and, then generating test ....

A. Ravara and V. Vasconcelos. Behavioural types for a calculus of concurrent objects. In 3rd International Euro-Par Conference, volume 1300 of Lecture Notes in Computer Science, pages 554-561. Springer, 1997.

....if seq ( ae seq (oe) A type ae not satisfying the conditions of Def. 7 is constructed for each reason [16] ut 5 Related Work Most work on types in concurrent systems is based on Milner s calculus [8, 7] and similar calculi. The problems of inferring most general types [4, 19] and subtyping [11, 12, 18, 3, 17] were considered. But these type systems cannot represent message sequences and ensure statically that all sent messages are acceptable. A large amount of work based on path expressions and process algebra shows that reasoning about the order of messages in concurrent systems is quite difficult. ....

A. Ravara and V. T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Proceedings Euro-Par '97, Lecture Notes in Computer Science. SpringerVerlag, 1997.

....calls or recursive message passing if there is danger that the recursion does not terminate. 5 RELATED WORK The majority of work on types for concurrent languages is based on Milner s calculus [8] and similar calculi. The problem of inferring most general types [4, 19] and subtyp ing [3, 6, 13, 17, 18] was considered. But these type systems differ in an important aspect from process types: The underlying calculi do not keep the message order. Not much work was done on type systems able to deal with constraints on the ordering of messages. Nierstrasz [11] proposes regular types and request ....

A. Ravara and V. T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Proceedings EuroPar '97, Lecture Notes in Computer Science. SpringerVerlag, 1997.

.... calculus [Mil91,MPW92] and similar calculi. Especially, the problem of inferring most general types was considered by Gay [Gay93] and Vasconcelos and Honda [VH93] Nierstrasz [Nie93] Pierce and Sangiorgi [PS93] Vasconcelos [Vas94] Colaco, Pantel and Sall e [CPS97] and Ravara and Vasconcelos [RV97] deal with subtyping. But their type models differ in an important aspect from the process type model: They cannot represent constraints on message sequences and ensure statically that all sent messages are acceptable; the underlying calculus does not keep the message order. The proposals of ....

Ant'onio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Proceedings Euro-Par '97, Lecture Notes in Computer Science. Springer-Verlag, 1997.

....right method for the message. Traditional type systems assign rigid interface like types to the names of the objects [13, 18, 6] Type systems that support objects with non uniform interfaces, based on the distinct de nition of a run time protocol error discussed above, have been proposed for TyCO [15, 16]. The systems ensure safety properties resulting from the absence of persistent bad redexes, namely the absence of some deadlocks (that we call local) and the guarantee that typable processes will not run into communication errors. Take the typical example of a one place bu er that only allows ....

Antonio Ravara and Vasco T. Vasconcelos. Behavioural Types for a Calculus of Concurrent Objects. In Euro-Par'97, volume 1300 of LNCS, pages 554-561. Springer Verlag, 1997.

....processes, the existence of principal types and of a type inference algorithm. In order to type communicating processes, recursive types are essential. They can be represented in several ways: as expressions with a recursion operator (e.g. in [21] as in nite trees [19] or as graphs [20, 23] (for di erent representations of recursive types for the calculus see [22] We chose graph representation for types as well as for processes. This enables us to establish a close correspondence between processes and types: there is a graph morphism from each process into its type. Thus, if a ....

Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Euro-Par '97. Springer-Verlag, 1997.

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Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Proc. of Euro-Par'97, LNCS 1300, pages 554--561. SpringerVerlag, 1997.

....requests. Let us initially concentrate on the rst. A process does not have a blocking, if all messages to its objects will eventually be accepted. Therefore, there must be a particular sequencing of the messages that allows their reception. Think of types as graphs, or as rational trees (cf. RV97] an object accepts a set of messages if, either its output type shares a path with its input type, or a path of one is a pre x of a path of the other. However, as the calculus is non deterministic, only when no sequencing of messages lead to blockings can one guarantee that the object accepts ....

Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Christian Lengauer, Martin Griebl, and Sergej Gorlatch, editors, 3th International Euro-Par Conference, number 1300 in Lecture Notes in Computer Science, pages 554-561. Springer-Verlag, 1997. Extended version available as DM-IST Research Report 06/97.

....Lopes, Silva and Vasconcelos Unbounded behavior is modeled through explicit instantiation of recursive templates. A type system assigns monomorphic types to variables and polymorphic types to template variables [25] Other type systems have been proposed that support non uniform object interfaces [20]. The calculus is reminiscent of the Abadi and Cardelli s calculus in the sense that objects are sums of labeled methods attached to names, the self parameters, and messages can be seen as asynchronous method invocations [3] TyCO is a very low level programming language with a few derived ....

Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Euro-Par'97, volume 1300 of LNCS, pages 554-561. Springer Verlag, 1997.

....(and synchronous) view of the objects that inhabit them. These ideas, along with the algebraic laws, are based on a notion of bisimulation that is unlike other notions in the literature. 1 Introduction Non uniform types for concurrent objects constitute the object of study of several authors [7, 2, 3, 6, 8]. The aim is to build type systems capable of ensuring more than the usual safety properties (such as subject reduction) for instance, the absence of some deadlocks. These types reflect a dependency of the interface of an object upon its internal state, conveying information about some dynamic ....

A. Ravara and V. Vasconcelos. Behavioural types for a calculus of concurrent objects. In 3rd International Euro-Par Conference, volume LNCS 1300, pages 554--561. Springer-Verlag, 1997.

....Lopes, Silva and Vasconcelos Unbounded behavior is modeled through explicit instantiation of recursive templates. A type system assigns monomorphic types to variables and polymorphic types to template variables [25] Other type systems have been proposed that support non uniform object interfaces [20]. The calculus is reminiscent of the Abadi and Cardelli s # calculus in the sense that objects are sums of labeled methods attached to names, the self parameters, and messages can be seen as asynchronous method invocations [3] TyCO is a very low level programming language with a few derived ....

Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Euro-Par'97, volume 1300 of LNCS, pages 554--561. Springer Verlag, 1997.

....conclusion, the objects behave similarly, but the rst implementation is more informative and more natural regarding the bu er s behaviour. For a thorough discussion on non uniform objects in T yCO see [24] We have been working on a theory of types able to accommodate this style of programming [26, 25]. In this work we incorporate and develop the idea of types as graphs [26] Our rst proposal of a looser notion of communication error is there, but it did not incorporate deadlock. We propose herein a syntactic view of the graph types, de ning a type algebra that provides a description of some ....

....informative and more natural regarding the bu er s behaviour. For a thorough discussion on non uniform objects in T yCO see [24] We have been working on a theory of types able to accommodate this style of programming [26, 25] In this work we incorporate and develop the idea of types as graphs [26]. Our rst proposal of a looser notion of communication error is there, but it did not incorporate deadlock. We propose herein a syntactic view of the graph types, de ning a type algebra that provides a description of some dynamic aspects of the behaviour of objects. Our types characterise the ....

[Article contains additional citation context not shown here]

Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In 3rd International Euro-Par Conference, volume LNCS 1300, pages 554-561. Springer-Verlag, 1997. Also available as Research report 6/97 DM-IST, Instituto Superior Tecnico.

....a nite (and small) number of such states, thus it is not dicult to program in this style. A more thorough discussion on non uniform objects in T yCO, with more complex examples, can be found elsewhere [26] We have been working on a theory of types able to accommodate this style of programming [27, 28]. We adopt a types as behaviours approach, such that a type characterises the semantics of a concurrent objects by representing all its possible life cycles as a state transition system. In this work we incorporate and develop the idea of types as graphs [28] Our rst proposal of a looser notion ....

....this style of programming [27, 28] We adopt a types as behaviours approach, such that a type characterises the semantics of a concurrent objects by representing all its possible life cycles as a state transition system. In this work we incorporate and develop the idea of types as graphs [28]. Our rst proposal of a looser notion of communication error is there, but it did not incorporate the detection of some deadlocks. Types are terms of a process algebra, fuelled by an higher order labelled transition system, providing an internal view of the objects that inhabit them. It ....

[Article contains additional citation context not shown here]

Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Proceedings of the 3rd International Euro-Par Conference, volume LNCS 1300, pages 554-561. Springer-Verlag, 1997. Also available as Research report 6/97 DM-IST, Instituto Superior Tecnico.

....method for the message. Traditional type systems assign rigid interface like types to the names of the objects [6, 13, 18] Type systems that support objects with non uniform interfaces, based on the distinct de nition of a run time protocol error discussed above, have been proposed for TyCO [15, 16]. The systems ensure safety properties resulting from the absence of persistent bad redexes, namely the absence of some deadlocks (that we call local) and the guarantee that typable processes will not run into communication errors. Take the typical example of a one place bu er that only allows ....

Antonio Ravara and Vasco T. Vasconcelos. Behavioural Types for a Calculus of Concurrent Objects. In Euro-Par'97, volume 1300 of LNCS, pages 554-561. Springer Verlag, 1997.

.... or disabled according to their internal state are very common in object oriented programming (e.g. a stack, a finite bu#er, an ftp server, a bank account, an automatic cash machine) Non uniform concurrent objects, and types able to cope with them, constitute the object of study of several authors [3, 10, 16, 17, 19, 21]. These types reflect a dependency of the interface of an object on its internal state, conveying information about dynamic properties of objects. The aim is to build type systems capable of ensuring not only the usual safety properties like subject reduction, but also more complex properties, ....

Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In 3rd International Euro-Par Conference, volume LNCS 1300, pages 554--561. Springer-Verlag, 1997.

....(and synchronous) view of the objects that inhabit them. These ideas, along with the algebraic laws, are based on a notion of bisimulation that is unlike other notions in the literature. 1 Introduction Non uniform types for concurrent objects constitute the object of study of several authors [7, 2, 3, 6, 8]. The aim is to build type systems capable of ensuring more than the usual safety properties (such as subject reduction) for instance, the absence of some deadlocks. These types reflect a dependency of the interface of an object upon its internal state, conveying information about some dynamic ....

A. Ravara and V. Vasconcelos. Behavioural types for a calculus of concurrent objects. In 3rd International Euro-Par Conference, volume LNCS 1300, pages 554--561. Springer-Verlag, 1997.

....j b C read : r] should not be considered an error, for the presence of a message b C write : u] makes the reception of the read message possible. The development of a type system able to type processes like the one above is the main motivation of this work. This paper is a short version of [RV97]. This work was partially supported by JNICT PRAXIS XXI projects 2 2.1 MAT 46 94 Escola, 2 2.1 MAT 262 94 SitCalc and 2 2.1 TIT 1658 95 LogComp, and by the ESPRIT Working Groups 22704 ASPIRE and 23531 FIREworks. 2 The calculus of objects TyCO is an object oriented name passing calculus with ....

A. Ravara and V. Vasconcelos. Behavioural types for a calculus of concurrent objects. Technical report DM-IST 6/97, Department of Mathematics, Instituto Superior T'ecnico, 1096 Lisboa, Portugal, 1997. Available from ftp://ftp.cs.math.ist.utl.pt/pub/RavaraA/97-R-BEVTYP.ps.gz.

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Antonio Ravara and Vasco T. Vasconcelos. Behavioural types for a calculus of concurrent objects. In Euro-Par '97. Springer-Verlag, 1997.

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