O. Nierstrasz. Towards an Object Calculus. In M. Tokoro, O. Nierstrasz, and P. Wegner, editors, Proc. of the ECOOP'91 Workshop Object-Based Concurrent Computing, pages 1--20. Springer-Verlag, LNCS 612, 1992.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....of the object. Dynamic communication channels allow to write methods that continue to work also when the value of the instance variable (that is, the reference) is modified. This greatly improves the flexibility of deductive objects and is in the main stream of object calculus and meta programming [55, 29]. The result of this paper is a clear, formal semantics of cooperating objects expressed as deductive databases preserving the simple computational model for Datalog language. This allows the reuse of the already developed results and techniques about expressive power and efficient query ....

....object oriented programming languages. Therefore, a major research direction is to extend the constraint language of deductive systems so that it can fit into the object oriented paradigm. Concurrency in object based systems has been investigated in the extended process algebra framework [35, 55]. By contrast, concurrency in logical systems is based on a theoretical approach developed specifically for this type of systems [56] In general, most concurrent logical languages consider concurrency among processes expressed as atoms in queries. The variables, shared among atoms, are ....

O. Nierstrasz. Towards an object calculus. In ECOOP '91 workshop on object-based concurrent computing, Lecture Notes in Computer Science, vol. 612, pages 1 20. Springer- Verlag, Berlin, 1991.

....and we have therefore focused on how to implement (in an abstract sense) broadcast communication when one to one asynchronous message passing is assumed. Recently in the (theoretical) object oriented community the asynchronous one to one message passing paradigm has been studied in its own right [13, 18]. Acknowledgement Acknowledgements are due to the anonymous Tapsoft referees for their insightful comments. ....

O. Nierstrasz. Towards an object calculus. In Proc. of the OOPSLA'90/ECOOP'91 workshop on Object-based concurrent computing, Gen`eve, Switzerland, 1991.

....of concurrent object oriented languages, e.g. 2, 20, 1, 4] has recently prompted the investigation of the theoretical foundations of concurrent objects. Several works provide encodings of objects in process calculi [19, 18, 12, 5] or, alternatively, supplement objects with concurrent primitives [16, 3, 11]. Those works promote a uni ed framework for reasoning about objects and processes, but they do not address the composition of object de nitions or its typechecking. In this work, we model concurrent objects in a simple process calculus a variant of the join calculus [7, 6] we design operators ....

....leave the state of the lock unchanged. In contrast with previous examples, the code above is quite general; it applies to any class following the same convention as bu for initialization. 5 Related and future works There are many works on supplementing object calculi with concurrent primitives [16, 3, 11], or on supplementing process calculi with objects (usually by the mean of an encoding in the original calculus) 19, 18, 12, 5] Our work follows the latter tradition. However, to our knowledge, it is the only one to address safe object composition in a process calculus. In [17] Odersky ....

O. Nierstrasz. Towards an object calculus. In O. N. M. Tokoro and P. Wegner, editors, Proceedings of the ECOOP'91 Workshop on Object-Based Concurrent Computing, LNCS 612, pages 1-20, 1992.

....t; f; x; y : S e S e 7 ( b : S p S p 7 (S e ; S e ) A key idea here is that sort information is assigned only to channels; processes are either well sorted under a particular set of assumptions for their bound and free names or they are not. This stands in contrast to recent proposals [17, 16] that attempt to assign more informative types to processes, describing the sets of channels on which processes may communicate, their interaction protocols, freedom from deadlock, etc. Also, this sort information is completely static: it does not describe the sequencing of values communicated ....

O. Nierstrasz. Towards an object calculus. In M. Tokoro, O. Nierstrasz, P. Wegner, and A. Yonezawa, editors, ECOOP '91 Workshop on Object Based Concurrent Programming, Geneva, Switzerland, 1991, volume 612 of Lecture Notes in Computer Science. Springer Verlag.

....objects can be viewed as processes, interactions among objects can be seen as communications, and encapsulation can be modeled by the restriction of visible communications. In [16] an executable notation for specifying concurrent object oriented languages has been explored in process calculus. In [17] some requirements for a calculus suitable for concurrent objects is presented. 14] presents a language based on a process calculus and analyzes the essential features of object based concurrency. Many theoretical models for real time computing have been explored in temporal logic, timed Petri ....

Nierstrasz,O.M., Towards an Object Calculus, In proceedings of ECOOP'91 Workshop on Concurrent Object-Based Concurrent Computing, LNCS, (ed.) Tokoro,M, Nierstrasz,O., and Wegner,P., LNCS, 1992.

....al 91, ISCORE] its impact on verification has yet to be fully explored. This paper is about foundational aspects of object oriented system verification. OBCC 91] provides a useful perspective of current trends in this direction. Most approaches are based on some form of process calculi (e.g. Nierstrasz 91] based on CCS and the p calculus) Other approaches rely on trace semantics and actor systems [Vasconcelos and Tokoro 91] The work around the languages POOL [America 89] and FOOPS [Goguen and Meseguer 87] must be singled out as being part of long term programmes of research around specific ....

O.Nierstrasz, "Towards an Object Calculus", in [OBCC 91], 1-20

....of concurrent object oriented languages, e.g. 2, 23, 1, 4] has recently prompted the investigation of the theoretical foundations of concurrent objects. Several works provide encodings of objects in process calculi [22, 20, 12, 6] or, alternatively, supplement objects with concurrent primitives [16, 3, 11]. Those works promote a uni ed framework for reasoning about objects and processes, but they do not address the composition of object de nitions or its typechecking. Microsoft Research, 1 Guildhall Street, Cambridge, U.K. y Dipartimento di Scienze dell Informazione, Universit a di Bologna, ....

....may be safely merged, thus leaving the space to separate compilation. Corollary 1 Chemical relations and preserve chemical typings modulo process reduction (i.e. taking 7 for ) 6 Related and future works There are many works on supplementing object calculi with concurrent primitives [16, 3, 11], or on supplementing process calculi with objects (usually by the mean of an encoding in the original calculus) 22, 20, 12, 6] Our work follows the latter tradition. However, to our knowledge, it is the only one to address safe object composition in a process calculus. In [17] Odersky proposes ....

O. Nierstrasz. Towards an object calculus. In O. N. M. Tokoro and P. Wegner, editors, Proceedings of the ECOOP'91 Workshop on ObjectBased Concurrent Computing, LNCS 612, pages 1-20, 1992.

.... the denotational approach, and by Astesiano et al. AGR92] in the setting of generalised algebraic specifications (we shall comment on these two works in the concluding section) by Nielson [Nie89] who has mainly focused on types as a means of ensuring more reliable programs; by Nierstrasz [Nie], who has tried to combine calculus and calculus with the purpose of defining a uniform framework for the semantics of concurrent object oriented languages; by Kennaway and Sleep [KS85] Strom and Yemini [SY85] Holmstrom [Hol83] Leth [Let92] Giacalone, Mishra, and Prasad [GMP89] whose ....

O. Nierstrasz. Towards an object calculus. In M. Tokoro, O. Nierstrasz, P. Wegner, and A. Yonezawa, editors, ECOOP '91 Workshop on Object Based Concurrent Programming, Geneva, Switzerland, 1991, volume 612 of Lecture Notes in Computer Science. Springer Verlag.

....of concurrent object oriented languages, e.g. 2, 22, 1, 4] has recently prompted the investigation of the theoretical foundations of concurrent objects. Several works provide encodings of objects in process calculi [21, 20, 13, 6] or, alternatively, supplement objects with concurrent primitives [17, 3, 12]. Those works promote a uni ed framework for reasoning about objects and processes, but they do not address the composition of object de nitions or its typechecking. In this work, we model concurrent objects in a simple process calculus a variant of the join calculus [8, 7] we design operators ....

....outside of its visibility scope. In order to express our result, we re ne the chemical semantics of section 2.3 to keep track of access privileges for every message along the reduction. 11 5 Related and future works There are many works on supplementing object calculi with concurrent primitives [17, 3, 12], or on supplementing process calculi with objects (usually by the mean of an encoding in the original calculus) 21, 20, 13, 6] Our work follows the latter tradition. However, to our knowledge, it is the only one to address safe object composition in a process calculus. In [18] Martin Odersky ....

O. Nierstrasz. Towards an object calculus. In O. N. M. Tokoro and P. Wegner, editors, Proceedings of the ECOOP'91 Workshop on Object-Based Concurrent Computing, LNCS 612, pages 1-20, 1992.

....be modeled by the restriction of visible communications. In [8] a formal system based on the notion of actor like object with asynchronous communication was investigated, and in [17] an executable notation for specifying concurrent object oriented languages in a process calculus was explored. In [18] some requirements for a calculus suitable for concurrent objects is presented. In [15] the author presents a language based on a process calculus and analyzes the essential features of object based concurrency. In [22] a semantics for POOL [1] is defined by the translation of the language ....

Nierstrasz, O. M., Towards an Object Calculus,In proceedings of ECOOP'91 Workshop on Concurrent Object-Based Concurrent Computing, LNCS 612, 1992.

....in process calculi [20, 19, 12, 7] or, vice versa, supplement objects Microsoft Research y Dipartimento di Scienze dell Informazione, Universit a di Bologna, Mura Anteo Zamboni 7, 40127 Bologna, Italy z INRIA Rocquencourt, BP 105, 78153 Le Chesnay Cedex France. with concurrent primitives [15, 4, 11]. In these works the interest is mostly the promotion of a unified framework for reasoning about objects and processes; in particular, none of these works address the composition of object definitions and its typing discipline. To achieve modularity of definitions of concurrent objects we promote ....

O. Nierstrasz. Towards an object calculus. In O. N. M. Tokoro and P. Wegner, editors, Proceedings of the ECOOP'91 Workshop on Object-Based Concurrent Computing, LNCS 612, pages 1--20, 1992.

....be modeled by the restriction of visible communications. In [8] a formal system based on the notion of actor like object with asynchronous communication was investigated, and in [17] an executable notation for specifying concurrent object oriented languages in a process calculus was explored. In [18] some requirements for a calculus suitable for concurrent objects is presented. In [15] the author presents a language based on a process calculus and analyzes the essential features of object based concurrency. In [22] a semantics for POOL [1] is defined by the translation of the language ....

Nierstrasz, O. M., Towards an Object Calculus, In proceedings of ECOOP'91 Workshop on Concurrent Object-Based Concurrent Computing, LNCS 612, 1992.

....program development time. In this paper, instead we propose an approach to dynamic message passing where the label is a variable and can be instantiated at execution time. Our approach greatly improves the flexibility of deductive objects and is in the main stream of object calculus, according to [8]. In our approach, methods expressed through rules, cooperate with objects which are not fixed. They can change over time according to different instances for variable labels. We call them generic methods. Unfortunately, this dynamicity is paid with more computation. Indeed, in X Obj U Datalog, ....

O. Nierstrasz. Towards an object calculus. In ECOOP '91 workshop on object-based concurrent computing, Lecture Notes in Computer Science, vol. 612, pages 1--20. Springer- Verlag, Berlin, 1991.

....uses Darwin [10] a configuration language given calculus semantics. The formal semantics of Darwin creates a platform for the specification and development of open, distributed systems. Recent research in formal methods has considered the theoretical underpinnings of concurrent object systems [15, 20, 23, 27]. Much of the work focuses on distributed systems, while other work consider the formal specification of concurrent object oriented programming (COOP) languages [4, 17, 30] The majority of them employ the calculus as a formal model for their languages. However, the calculus is not ....

....not well suited to modeling concurrently executing objects because it does not readily support complex message passing. The Robust Object Calculus (ROC) 29] developed at the University of Tulsa is a new formalism for concurrently executing objects. It is based on Nierstrasz s Object Calculus (OC) [27], but extends it by providing robust agent encapsulation. Such a formalism is needed to provide the foundation for practical distributed system verification. While ROC is well suited to providing formal operational semantics for distributed object systems, a more expressive logic is required for ....

[Article contains additional citation context not shown here]

O. Nierstrasz. Towards an object calculus. In M. Tokoro, O. Nierstrasz, P. Wegner, and A. Yonezawa, editors, Proceedings of the ECOOP '91 Workshop on Object-Based Concurrent Computing, pages 1--20, Amsterdam, The Netherlands, 1991. Springer-Verlag.

....recently, Satoh and Tokoro developed RtCCS [59] a formalism for real time ob ject oriented computing based on ccs. For these dioeerent approaches, sound type sys tems were developed [4, 49, 65, 35] and formal semantics have been described in dioeerent frame works (denotational [6] operational [5, 48, 3, 19], based on the calculus [67] or traces [64] Based on a formal model or not, several concur rent object oriented programming languages have been designed, such as ConcurrentSmalltalk [72] Distributed Smalltalk [11] Hybrid [45] Pool [4] ABCL [68] Eioeel [16] DROL [63] and more re ....

O. Nierstrasz. Towards an object calculus. In Proc. of the ECOOP '91 Workshop on Object-Based Concurrent Computing, LNCS 612, pages 120. Springer-Verlag, 1992.

.... The operator based approach advocated in Jigsaw seems to fit well with process calculus models of concurrency in the style of CCS [61] Nierstrasz has investigated such calculi in an object oriented context [57] More recent work by Nierstrasz investigates the integration of process and calculi [56]. In [56] it is shown how to express the fixpoint operator in such an integrated calculus. It should therefore be possible to integrate Jigsaw style generator definitions into this framework. This leads toward the exciting possibility of an expression based language for composing modular, ....

.... based approach advocated in Jigsaw seems to fit well with process calculus models of concurrency in the style of CCS [61] Nierstrasz has investigated such calculi in an object oriented context [57] More recent work by Nierstrasz investigates the integration of process and calculi [56] In [56], it is shown how to express the fixpoint operator in such an integrated calculus. It should therefore be possible to integrate Jigsaw style generator definitions into this framework. This leads toward the exciting possibility of an expression based language for composing modular, concurrent ....

Nierstrasz, O. Towards an object calculus. In ECOOP'91 Workshop on Object-based Concurrent Computing (July 1991).

.... as a foundation for designing various concurrent object oriented languages (e.g. ABCL [Yon90] and [FA93] Theoretical research using this model has focused on semantics and equational theories (e.g. AMS92, Tal96] The process algebra approaches to modeling concurrent object oriented systems [PT94, Vas94, Nie92, KY94, Jon93] are often extensions of the calculus, obtained by adding objects and functional constructs. Researchers adopting this approach have paid particular attention to typing issues (c.f. Vas94, KY94] Both the actor and the process algebra approaches suffer from not directly supporting objects, a ....

O. Nierstrasz. Towards an object calculus. In Proc. of the ECOOP'91 Workshop on Object-Based Concurrent Computing, 1992.

....61] The Regis distributed system uses Darwin [16] a configuration language with calculus semantics. Darwin provides a platform for the specification of open, distributed systems. 16 Recent research in formal methods has considered the theoretical underpinnings of concurrent object systems [29, 40, 44, 50]. Much of the work focuses on distributed systems, while other work considers the formal specification of concurrent object oriented programming languages (COOPLs) 4, 32, 61] The majority of them employ the calculus as a formal model for their languages. However, the calculus is not ....

....is not well suited to modeling concurrently executing objects because it does not readily support complex message passing. The Robust Object Calculus (ROC) 60] developed at the University of Tulsa is a new formalism for concurrently executing objects. It extends Nierstrasz s Object Calculus (OC) [50] by providing robust agent encapsulation. Such a formalism is needed to provide the foundation for practical distributed system verification. While ROC is well suited to providing formal operational semantics for distributed object systems, a more expressive logic is required for reasoning and ....

[Article contains additional citation context not shown here]

O. Nierstrasz. Towards an object calculus. In M. Tokoro, O. Nierstrasz, P. Wegner, and A. Yonezawa, editors, Proceedings of the ECOOP '91 Workshop on Object-Based Concurrent Computing, pages 1--20, Amsterdam, The Netherlands, 1991. Springer-Verlag.

....developed to allow processes themselves to be treated as first class values, an abstraction feature enjoyed by the calculus. HO maps to calculus using denotational semantics and suffers from the same practical problems listed above. The OC (Object Calculus) language was developed by Nierstrasz [21] and inherited the nice features of HO , plus the functional application feature of calculus. Furthermore, OC adds complex messaging and the ability to override default behavior by introducing a deterministic choice operator (left preferential choice) OC has a major flaw in that it lacks a way ....

....the notation afv=xg is used to denote that all wildcards in x are replaced by the corresponding subvalues of v in the agent a. For example, when v# binds to n in a, each free occurrence of n in a is replaced by v. 3.2. 3 ROC Syntax The ROC syntax is derived from Nierstrasz s Object Calculus (OC) [21]. The symbol # distinguishes bindable values from unbindable values. The non deterministic choice operator from calculus is added. The BNF syntax is shown below. a : a a (concurrent composition) j n : a (recursion) j a a (non deterministic choice) j a j a (left preferential ....

[Article contains additional citation context not shown here]

O. Nierstrasz. Towards an object calculus. In M. Tokoro, O. Nierstrasz, P. Wegner, and A. Yonezawa, editors, Proceedings of the ECOOP '91 Workshop on Object-Based Concurrent Computing, pages 1--20, Amsterdam, The Netherlands, 1991. Springer-Verlag.

....messages, or it may silently change state by means of an internal communication. Communication events take place when there are matching input and output offers between concurrent agents. The behaviour of agents may be described precisely by a simple language, or object calculus, called OC [13]. It is possible to define higher level abstractions such as remote procedure calls, various synchronization mechanisms, control structures, classes, and even inheritance, as patterns, that is, as functions over the space of agents. Since OC is an executable language, it can serve simultaneously ....

O. Nierstrasz, "Towards an Object Calculus," in Proceedings of the ECOOP '91 Workshop on Object-Based Concurrent Computing, ed. M. Tokoro, O. Nierstrasz, P. Wegner, A. Yonezawa, LNCS, Springer-Verlag, Geneva, Switzerland, July 15-16, 1991, to appear.

....to a given architectural style. The composition language we propose is an experimental prototype currently under development. To address open, distributed systems, it is based on an object model in which objects and components map to a formal abstract machine integrating processes and functions [28]. The mapping is also the basis for the experimental prototype, as the abstract machine is itself executable. Our development strategy is highly experimental, and we expect the language design to evolve rapidly as the result of our application experiments. One of our goals is to use the ....

....to the monadic calculus. The higher order p calculus is a close fit to our requirements and appears to be an excellent basis for developing a formal model of objects and components. Already, there have been some attempts to develop an object calculus based on variants of the p calculus [12] [28], and some researchers have experimented with modeling object oriented language features in the p calculus [35] So far, however, there is no standard model of objects as processes, and the relative advantages and disadvantages of the possible mappings have not be systematically catalogues or ....

[Article contains additional citation context not shown here]

Oscar Nierstrasz, "Towards an Object Calculus," Proceedings of the ECOOP '91 Workshop on Object-Based Concurrent Computing, M. Tokoro, O. Nierstrasz, P. Wegner (Ed.), LNCS 612, Springer-Verlag, 1992, pp. 1-20.

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O. Nierstrasz. Towards an Object Calculus. In M. Tokoro, O. Nierstrasz, and P. Wegner, editors, Proc. of the ECOOP'91 Workshop Object-Based Concurrent Computing, pages 1--20. Springer-Verlag, LNCS 612, 1992.

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O. Nierstrasz. Towards an object calculus. In M. Tokoro, O. Nierstrasz, and P. Wegner, editors, Proceedings of the ECOOP'91 Workshop on Object-Based Concurrent Computing, volume 612 of LNCS, pages 1--20. Springer-Verlag, 1992.

No context found.

O. Nierstrasz. Towards an object calculus. In O. N. M. Tokoro and P. Wegner, editors, Proceedings of the ECOOP'91 Workshop on Object-Based Concurrent Computing, LNCS 612, pages 1-20, 1992.

No context found.

O. Nierstrasz. Towards an object calculus. In M. Tokoro, O. Nierstrasz, P. Wegner, and A. Yonezawa, editors, ECOOP '91 Workshop on Object Based Concurrent Programming, Geneva, Switzerland, 1991. , volume 612 of Lecture Notes in Computer Science. Springer Verlag.

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