Uwe Nestmann, Hans Huttel, Josva Kleist, and Massimo Merro. Aliasing models for mobile objects. Accepted for Journal of Information and Computation. Available from http://www.cs.auc.dk/research/FS/ojeblik/. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, LNCS 1685, 2000.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....text, and not by the execution site. Since Obliq is lexically scoped, we can ignore the aspects of distribution provided that sites do not fail; site failure would allow clients to trivially observe whether an object on one site has moved to another site. Following this idea, we focus on jeblik [23], an object based language that represents Obliq s concurrent core, but can also be seen as a concurrent extension of the Imperative Object Calculus [1] jeblik supports a distribution free abstraction of migration called surrogation. Like migration, the surrogation of an object a is described as ....

....into a proxy for b, which forwards future request for methods of a to b. The main di#erence with respect to migration is that neither a nor b are attached to any site. Consequently, a. surrogate a results in a pointing to its clone b. a b 2 Correctness as an equation. In [23], we motivated a precise definition of correctness for object surrogation in jeblik. The intuition is that the surrogation of an object must be transparent to the clients of that object. It is formalised by means of an equation: x.ping; x . x.surrogate; x (1) where x is supposed to be a ....

[Article contains additional citation context not shown here]

Uwe Nestmann, Hans Huttel, Josva Kleist, and Massimo Merro. Aliasing models for mobile objects. Accepted for Journal of Information and Computation. Available from http://www.cs.auc.dk/research/FS/ojeblik/. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, LNCS 1685, 2000.

....to reason about terms, i.e. programs in the source language. We have recently experimented with some non trivial OOL (OO language) derived from Obliq [1] as a subset including concurrency, cloning, and aliasing, which is enough to simulate a particular style of mobile objects within the language [4]. In order to prove, using an algebraic equation within the object language, that this style of object migration can be carried out in a safe manner [3] we used a semantics by translation into an enhanced Local # calculus [2] Among the many things learned from this non trivial exercise of using ....

U. Nestmann, H. Huttel, J. Kleist, and M. Merro. Aliasing models for mobile objects. Accepted for Journal of Information and Computation. Available from http://www.cs.auc.dk/ research/FS/ojeblik/. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, LNCS 1685, 2000.

....results as well as the proofs accessible also to readers not familiar with process calculi. Furthermore, we strengthen our former results by using, in addition to may equivalence, the much more distinguishing notion of must equivalence. 1. Introduction This paper addresses, like previous works [NHKM01, MKN00], the problem of expressing the mobility of objects in lexically scoped languages like Obliq [Car95] by means of cloning and aliasing. In this sense, it is to be seen as a natural continuation of these works. 1 2 The title of this paper is intended to emphasize two different messages. Firstly, ....

....proxies. Thus, our study is not only addressing Obliq, but any language that supports a blocking strategy for transparent object migration using proxies. Previous Work. We have studied in great detail the problems of developing and exploiting formal semantics of languages arising from Obliq. In [NHKM01], guided by an implementation of Obliq, we studied four different operational semantics and formalized safe migration as the following theorem: in x.ping # = x.surrogate we equate (with respect to a large class of program contexts) the program x.ping, which just witnesses the responsiveness of ....

[Article contains additional citation context not shown here]

U. Nestmann, H. Httel, J. Kleist and M. Merro. Aliasing Models for Mobile Objects. Accepted for Journal of Information and Computation. Available from http://www.cs.auc.dk/research/FS/ojeblik/. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, LNCS 1685, 2001.

....the results and the proofs accessible also to readers not familiar with process calculi. Furthermore, we strengthen our former results by using, in addition to may equivalence, the much more distinguishing notion of must equivalence. 1. Introduction This paper addresses, like previous works [NHKM00, MKN00], the problem of expressing the mobility of objects in lexically scoped languages like Obliq [Car95] by means of cloning and aliasing. In this sense, it is to be seen as a natural continuation of these works. 1 2 The title of this paper is intended to emphasize two different messages. Firstly, ....

....namely the fact that clients cannot observe the difference between an the cases where an object has moved or not (yet) even not up to must equivalence . Previous Work. We have studied in great detail the problems of developing and exploiting formal semantics of languages arising from Obliq. In [NHKM00], guided by an implementation of Obliq, we studied four different operational semantics and formalized safe migration as the following theorem: in x.ping # = x.surrogate we equate (with respect to a large class of program contexts) the program x.ping, which just witnesses the responsiveness of ....

[Article contains additional citation context not shown here]

U. Nestmann, H. Httel, J. Kleist and M. Merro. Aliasing Models for Mobile Objects. Accepted for Journal of Information and Computation. Available from http://www.cs.auc.dk/research/FS/ojeblik/. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, LNCS 1685, 2000.

....Obliq is lexically scoped, we can ignore the aspects of distribution, at least when regarding the results of Obliq computations, unless sites fail. In the latter case, clients can trivially observe whether an object on one site has moved to another site. Following this idea, we focus on jeblik [NHKM00] an object based language that represents Obliq s concurrent core, but can also be seen as a concurrent extension of the Imperative Object Calculus [AC96] jeblik supports a distribution free abstraction of migration called surrogation. Like migration, the surrogation of an object a is ....

....into a proxy for b, which forwards future request for methods of a to b. The main di erence with respect to migration is that neither a nor b are attached to any site. Consequently, a. surrogate a results in a pointing to its clone b. # # # # # # # # a ## b 1 Correctness as an equation In [NHKM00] we motivated a precise de nition of correctness for object surrogation in jeblik. The intuition is that the surrogation of an object must be transparent to the clients of that object. It is formalised by means of an equation: x.ping; x . x.surrogate; x (1) where x is supposed to be a ....

[Article contains additional citation context not shown here]

U. Nestmann, H. Huttel, J. Kleist and M. Merro. Aliasing Models for Mobile Objects. Accepted for Journal of Information and Computation. Available from http://www.cs.auc.dk/research/FS/ ojeblik/. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, LNCS 1685, 2000.

....is completely determined by their location in the program text, and not by the execution site. Since Obliq is lexically scoped, we can ignore the aspects of distribution, at least when regarding the results of Obliq computations, unless sites fail. Following this idea, we focus on jeblik [NHKM00] an object based language that represents Obliq s concurrent core, but can also be seen as a concurrent extension of the Imperative Object Calculus [AC96] jeblik supports a distribution free abstraction of migration called surrogation. Like migration, the surrogation of an object a is ....

....of an object a is described as the creation of a clone b of a and then turning a itself into a proxy for b, which forwards future request for methods of a to b. The main di erence with respect to migration is that neither a nor b are attached to any site. Correctness as an equation In [NHKM00] we gave a formal de nition of correctness for object surrogation in jeblik which can be straightforwardly adapted to object migration in Obliq. The intuition is that, in order to be correct, the surrogation of an object must be transparent to the clients of that object, i.e. the object must ....

[Article contains additional citation context not shown here]

U. Nestmann, H. Huttel, J. Kleist and M. Merro. Aliasing Models for Mobile Objects. Accepted for Journal of Information and Computation. Available from http://www.cs.auc.dk/research/FS/ ojeblik/. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, LNCS 1685, 2000.

....reason about terms, i.e. programs in the source language. We have recently experimented with some non trivial OOL (OO language) derived from Obliq [Car95] as a subset including concurrency, cloning, and aliasing, which is enough to simulate a particular style of mobile objects within the language [NHKM00]. In order to prove, using an algebraic equation within the object language, that this style of object migration can be carried out in a safe manner [MKN00] we used a semantics by translation into an enhanced Local calculus [Mer00] Among the many things learned from this non trivial exercise ....

U. Nestmann, H. Huttel, J. Kleist and M. Merro. Aliasing Models for Mobile Objects. Accepted for Journal of Information and Computation. Available from http://www.cs.auc.dk/ research/FS/ojeblik/. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, LNCS 1685, 2000.

....Since Obliq is lexically scoped, we may ignore the aspects of distribution, at least when regarding the results of Obliq computations, unless distribution sites fail. Following this idea, jeblik, which we introduce in Section 3, is an object based language that represents Obliq s concurrent core [16], but it can also be seen as a concurrent extension of the Imperative Object Calculus [1] jeblik supports surrogation, a distribution free abstraction of migration. A draft full paper is available at http: www.cs.auc.dk research FS ojeblik Supported by Marie Curie fellowhip, EU TMR, ....

....surrogation, a distribution free abstraction of migration. A draft full paper is available at http: www.cs.auc.dk research FS ojeblik Supported by Marie Curie fellowhip, EU TMR, No. ERBFMBICT983504. Basic Research in Computer Science, Danish National Research Foundation. In [16] we gave a formal de nition of correctness for object surrogation in jeblik which can be straightforwardly extended to object migration in Obliq. The intuition is that, in order to be correct, the surrogation (resp. migration) of an object must be transparent to the clients of that object, i.e. ....

[Article contains additional citation context not shown here]

U. Nestmann, H. Huttel, J. Kleist, and M. Merro. Aliasing Models for Mobile Objects. Accepted for Journal of Information and Computation. An extended abstract has appeared as Distinguished Paper in the Proceedings of EUROPAR '99, pages 1353-1368, LNCS 1685, September 1999, 1999.

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