O. Nierstrasz and M. Papathomas. Towards a type theory for active objects. ACM OOPS Messenger, Proceedings OOPSLA/ECOOP 90 Workshop on Object-Based Concurrent Systems, 2(2):89--93, Apr. 1991.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....In [7] the author favors this manner of synchronization overriding. There is, however, no general agreement on this issue. As an example the language Rosette [26]is based on making synchronization constraints less strict in the derived classes, and other authors argue in favor of this choice [23, 22]. In Jeeg both manners of synchronization overriding are possible, indeed we believe that both techniques have their use in di#erent situations. As an example of a derived class which makes the synchronization constraints of the parent less stringent consider the a simple class representing a ....

O. Nierstrasz and M. Papathomas. Towards a type theory for active objects. ACM OOPS Messenger, Proceedings OOPSLA/ECOOP 90 Workshop on Object-Based Concurrent Systems, 2(2):89--93, Apr. 1991.

....In [7] the author favors this manner of synchronization overriding. There is, however, no general agreement on this issue. As an example the language Rosette [24] is based on weakening the synchronization constraints in the derived classes, and other authors argue in favor of this choice [21, 20]. In Jeeg both manners of synchronization overriding are possible, indeed we believe that both techniques have their use in di erent situations. As an example of a derived class which makes the synchronization constraints of the parent less stringent consider the a simple class representing a ....

O. Nierstrasz and M. Papathomas. Towards a type theory for active objects. ACM OOPS Messenger, Proceedings OOPSLA/ECOOP 90 Workshop on Object-Based Concurrent Systems, 2(2):8993, Apr. 1991.

....in addition to the case above. The decision of whether a role or an object is able to configure a particular role should then be based upon some type conformance relation of labeled transition systems. An attempt to establish such a relation, denoted interaction conformance, is discussed in [Nierstrasz91] This work is related to the work on CCS (Calculus of Communicating Systems) by [Milner] among others. We are working on establishing such a type conformance relation for different kinds of message semantics. In section 4 we are not being very accurate concerning differences in the programming ....

O.Nierstrasz, M.Papathomas, Towards a Type Theory for Active Objects, OOPS Messenger, Vol.2, No.2, April 1991, pp.89-93

.... Note: base class constructor is executed first HybridLinearOrd( B 1 = B i ; B i = B i outPair; B n = B n outPair; become nextBehavior( FIGURE 2. Hybrid Linear Order Class Definition. 12 tured by the behavior function. Interesting work in this area is [Nierstrasz 90] which also uses CCS as a starting point. We have not discussed the details of the run time enforcement of behavior sets. ACT and behavior sets have been implemented on the Sequent Symmetry, a shared memory multiprocessor Kafura 93] A subject of our current research is to determine the ....

Oscar Nierstrasz and Michael Papathomas. "Towards a type theory for active objects," in Object Management, pp. 295-304, (ed. D. Tsichritzis), Centre Universitaire D'Informatique, Universite De Geneva, 1990.

....from class definition, over the alternative of modeling behavioural relationships as classes [Sullivan and Notkin, 1991] We have identified a number of open issues in the design of a language supporting our model. Chief among these is development of a type theory for plug compatibility of aspects [Nierstrasz and Papathomas, 1990]. Type conformance to slots is the only limitation placed on a sub components use. Subcomponents may, for example, originate from unrelated code bases. Type information for each sub component is required beyond compile time that describes its behaviour. Signatures do not provide enough information ....

....may, for example, originate from unrelated code bases. Type information for each sub component is required beyond compile time that describes its behaviour. Signatures do not provide enough information about the behaviour of an object to determine if it is safe to use in a new context [Nierstrasz and Papathomas, 1990]. Some information will be needed about how it appears to behave externally when exposed to particular events. Furthermore, ECO objects may dynamically modify their interface (through subscription and unsubscription of events) To extend our analogy, an sub component s shape may vary over time. ....

Nierstrasz, O. and Papathomas, M. (1990). Towards a type theory for active objects. In Conference on Object-Oriented Programming: Systems,Languages, and Applications/European Conference on Object-Oriented Programming. OOPSLA/ECOOP, ACM Press.

....represent the channel by which the results of method execution exit. For instance, the parameters (data, aWDg, delay) of compute are transfered from the input 2 of the global component to the input 3 of the Watched object. These notions are closely akin to plug compatibility concept described in [9] and to signatures composed of a method names set, with their arguments and their types and moreover, in our case, with the events received and emitted by the object. 4 5 3 2 1 7 6 3 2 1 4 3 1 2 Reactive part Transformational part Watched object Watchdog ccompute Dcompute Rcompute Rcompute ....

O. Nierstrasz and M. Papathomas. "Towards a type theory for active objects". OOPS Messenger, 2(2):89--93, 1991.

....with inheritance, but this is included in Chat. Walk] do not consider errors which can occur when sending a message to an object for which the receiver have no corresponding method. This is handled above in the Smalltalk way by sending the receiver the message messageNotUnderstood. Nier1] and [Nier2]] define object behaviour using Abacus [Nier3] which is based on Milner s CCS [Mil1] and Hoare s CSP [Hoare] Systems with dynamic intercommunication structure or dynamic linkage are not directly representable in these languages so they only describe static aspects. This limitation is something ....

....Smalltalk turns quasi parallel objects into entities which may execute in real parallel, perhaps on parallel hardware and there by exploiting the hardwares computing powers something which is hard to do when having to make a program design based on a sequential programming language paradigm. In [Nier2] an object type theory is presented based on a labelled transition system. For future work a similar approach to typing of objects could be studied based on the definition of bisimulation in [Mil2 3] Future work may also be to prove by bisimulation that delegation and inheritance can express the ....

Oscar Nierstrasz, Michael Papathomas,Toward a Type Theory for Active Objects, in Object Management, ed. D.C. Tsichritzis, Centre Universitaire d'Informatique, University of Geneva, July 1990

....process calculi which passes processes [21, 4] 2) The most important possibility of our formal construction in the pragmatic context may exist in sound formulation of the notion of types for concurrent objectbased computing. There is an interesting work in this direction by Nierstrasz [19]. We hope that the study of asynchronous semantics will provide us with suggestions for typed programming for concurrent objects. Finally the authors would like to thank Carl Hewitt, who stayed in Keio University from Autumn 1989 to Summer 1990, for beneficial discussions with them, to Professor ....

Nierstrasz, O. : Towards a Type Theory for Active Objects. in [25].

....Actor language [7] The view that synchronization constraints get increasingly more restrictive in subclasses has proven useful in practice. It may seem that our notion of increasingly restrictive synchronization constraints may violate substitutability properties of subclasses. In [15] and [14], for example, it is argued that subclasses should contain at least the input offers of superclasses, implying that synchronization constraints get increasingly less restrictive in subclasses. The motivation for this approach is subtype substitutability in the following sense: the type of a ....

O. Nierstrasz and M. Papathomas. Towards a Type Theory for Active Objects. In D. Tsichritzis, editor, Object Management. University of Geneva, 1990.

....[25] 26] At the abstraction level, however, we lack good formalisms for reasoning about the abstract behaviour of concurrent objects. A step in this direction is to develop a notion of plug compatibility for the composition of objects based on the interactions between servers and clients [27]. The specification of the behavioural contracts [13] between collections of cooperating objects is a promising approach. Finally, the earnest evaluation of language design choices depends on the ability to formalize the semantics of various language constructs and the ability to rapidly ....

O.M. Nierstrasz and M. Papathomas, "Towards a Type Theory for Active Objects," in Object Management, ed. D.C. Tsichritzis, pp. 295-304, Centre Universitaire d'Informatique, University of Geneva, July 1990.

....of classes relative to subclasses are aggravated in the concurrent case [22] 3. Compositionality of concurrent objects is poorly understood. Standard notions of polymorphism do not carry over very well to the world of concurrent objects that may exhibit non uniform service availability [29, 31]. To address these issues, we propose the development of an object calculus that integrates the concept of agents present in process calculi with that of functions present in calculi. An (active) object can then be viewed as a function (agent) with state. Mechanisms for software composition can ....

O.M. Nierstrasz and M. Papathomas, "Towards a Type Theory for Active Objects," ACM OOPS Messenger, Proceedings OOPSLA/ECOOP 90 workshop on Object-Based Concurrent Systems, vol. 2, no. 2, pp. 89-93, April 1991.

....it is necessary to know more about the client s expectations. We have previously explored interaction equivalence with respect to the expectations of particular sets of observers, and found that equivalence with respect to all possible observers (also) reduces to failures equivalence [27]. We expect that relativizing request substitutability with respect to the expectations of specific classes of clients will lead to more general and more useful results for the case of multiple concurrent clients. 4.8 Open Problems We have proposed service types as a means of characterizing the ....

Oscar Nierstrasz and Michael Papathomas, "Towards a Type Theory for Active Objects," ACM OOPS Messenger, Proceedings OOPSLA/ECOOP '90 Workshop on Object-Based Concurrent Systems, vol. 2, no. 2, April 1991, pp. 89--93.

....temporal logic [16] using abstract states to express the external behaviour of an object in terms of liveness and safety conditions. We are presently investigating the properties of interaction conformance, which characterizes agents in terms of their possible interactions with a set of observers [25]. 6. Concluding Remarks The clean integration of concurrency features into object oriented languages is still an open problem. We have proposed a reference model for the design of concurrent object oriented languages based on communicating agents, and we have presented a compact executable ....

....Developing a pattern language that will permit syntactic patterns to be bound to behavioural patterns in Abacus. Developing a polymorphic type model for concurrent objects that partially specifies the behaviour of objects in terms of safety and liveness conditions over interactions with clients [25]. Viewing Objects as Patterns of Communicating Agents ....

O.M. Nierstrasz and M. Papathomas, "Towards a Type Theory for Active Objects," in Object Management, ed. D.C. Tsichritzis, Centre Universitaire d'Informatique, University of Geneva, July 1990, (Working Paper).

....it is necessary to know more about the client s expectations. We have previously explored interaction equivalence with respect to the expectations of particular sets of observers, and found that equivalence with respect to all possible observers (also) reduces to failures equivalence [24]. We expect that relativizing request substitutability with respect to the expectations of specific classes of clients will lead to more general and more useful results for the case of multiple concurrent clients. 8 Open Problems We have proposed service types as a means of characterizing the ....

Oscar Nierstrasz and Michael Papathomas, "Towards a Type Theory for Active Objects," ACMOOPS Messenger, Proceedings OOPSLA/ECOOP 90 Workshop on Object-Based Concurrent Systems, vol. 2, no. 2, April 1991, pp. 89-93.

No context found.

O. Nierstrasz and M. Papathomas. Towards a type theory for active objects. ACM OOPS Messenger, Proceedings OOPSLA/ECOOP 90 Workshop on Object-Based Concurrent Systems, 2(2):89--93, Apr. 1991.

No context found.

O. Nierstrasz and M. Papathomas. Towards a type theory for active objects. ACM OOPS Messenger, Proceedings OOPSLA/ECOOP 90 Workshop on Object-Based Concurrent Systems, 2(2):89--93, Apr. 1991.

No context found.

O. Nierstrasz and M. Papathomas. #Towards a type theory for active objects," in Object Management, #ed. D. Tsichritzis#, pp. 295#304, Centre Universitaire D'Informatique, Universit#e De Geneva, 1990.

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