J. Meseguer. A logical theory of concurrent objects. ACM SIGPLAN Notices, 25#10#:101#115, Oct 1990. Proc. OOPSLA#ECOOP '90.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....logic [9] is another true concurrent model: it aims at describing a wide variety of concurrent systems. While there is some work done on concurrent semantics for process calculi such as CCS ( 3] discusses and compares three of them) and for Petri nets (e.g. 1, 5, 7] except for Meseguer s work [10], not much work on concurrent semantics for objects has been done. We propose a concurrent semantics for actor systems, based on the theory of traces [1, 5, 7] The theory of traces introduced in computer science by Mazurkiewicz [8] to describe the behavior of safe Petri nets views concurrent ....

Jos'e Meseguer. A logical theory of concurrent objects. In OOPSLA/ECOOP, pages 101--115, ACM Press, October 1990.

....[6] list a number of features which they argue are essential for OO database systems. Parallel to this, a number of formalizations of OO models have been proposed, such as COL [1, 2, 3] F logic [33] HILOG [13] ILOG [29] IQL [4, 5] formalizations of 02 [36, 35] OBJ and related languages [20, 21, 22, 23, 25, 38], OBLOG [15, 19, 17, 43] and CMSL [50, 46] Beeri [9] gives a survey of some issues. Even though these papers are top down, there is not yet any root concept from which they develop their formalization of object orientation. The trees of possibilities they explore have different roots and are ....

J. Meseguer. A logical theory of concurrent objects. In N. Meyrowitz, editor, Object-Oriented Programming: Systems, Languages and Applications/European Conference on Object-Oriented Programming, pages 101 115, October 1990.

....Linear Logic has been exploited to account for concurrency also in [1, 17] however, the background there is functional programming, instead of logic programming. 14] exploits the intuitionistic (sequential) version of Linear Logic to refine the control mechanisms of sequential logic programs. [20] describes a general framework for rewriting logics , suitable for accounting for change in a concurrent programming context. 22] approaches the problem of locality of interaction among concurrent subsystems from the point of view of process algebras. 5 Open Problems Our main effort is ....

J. Meseguer. A logical theory of concurrent objects. In Proc. of OOPSLA/ECOOP'90, 1990. 15

....language Maude is based upon both equational and rewriting logic. Maude s equational logic, called membership equational logic, is an extension of OBJ3 s order sorted equational logic (the sorts can be ordered by a partial order relation) and its operational semantic is based on rewriting logic [21]. Maude functional modules are executed by interpreting the equations of a specification as a left to right term rewriting system. This reduction process finishes when a term is reached to which no equation can be applied. The resulting term is named the canonical term and the term algebra ....

J. Meseguer, "A logical theory of concurrent objects", Proc. of ECOOP-OOPSLA'90 Conf. on Object-Oriented Programming, Ottawa, Canada, ACM, October 1990, pp.101115.

....variables, through which local entities may communicate. One may describe communication via synchronous message passing, as in the language POOL, see [3] Here we sketch asynchronous communication where there is a global collection of messages waiting to be executed. Related ideas are expressed in [4, 17, 2]. This collection in a sense is a substitute for the global state; it may be depicted as a sea or chemical soup of messages, in which each object can recognize the messages directed at it through uniqueness of identifiers. Thus each object can pick out the relevant messages from this soup, ....

J. Meseguer. A logical theory of concurrent objects. In N. Meyrowitz, editor, OOPSLA, ECOOP'90 Proceedings, pages 101--115. ACM, 1990.

.... and we need to have eOEcient proof search methods for the logic we consider, for example based on specic proof schemas as uniform proofs in [14, 33] or canonical proofs [8, 11] Other proposals are based on rewriting logic as a unied model of concurrency and as a theory of concurrent objects [25]. In fact we have two main goals in this paper. The rst one is to motivate the interest of the use of fragments of LL for concurrent object programming, for example with a process calculus where the basic mechanisms are at the logical level. This last point leads to the question of using logic ....

J. Meseguer. A logical theory of concurrent objects. In OOPSLA-ECOOP '90, pages 101115, Ottawa, October 1990. Sigplan Notices, (25), 10.

....rules of the form (y) namely we can associate object identifiers with specific addresses in the virtual address space of a parallel machine and can then send messages addressed to an object to its corresponding addres. The above representation of objects is the one adopted in the Maude language [72, 83, 76]. It assumes, as it is common in many object oriented systems, that each object has a unique name, different from that of all other objects. In 5 Note that rewrite rules for natural number addition have also been applied. fact, by giving appropriate rewrite rules for the creation and deletion of ....

Jos'e Meseguer. A logical theory of concurrent objects. In ECOOP-OOPSLA'90 Conference on Object-Oriented Programming, Ottawa, Canada, October 1990, pages 101--115. ACM, 1990.

....proof tasks are essential for speeding up formal verification and making proofs more reliable and partly automatic. 4 Operational Semantics Many approaches have been suggested to define the semantics of objectoriented languages. Most approaches define semantics in terms of mathematical models [1,19,8]. An exception is [18] which define semantics in terms of a process calculus [22] based on operational semantics [23] Because of the lack of a fully abstract mathematical model for interleaving, and the intrinsic details of the semantics of object identification and dynamic object creation and ....

Meseguer, Jos'e, A logical theory of concurrent objects, in: Proceedings of ECOOP-OOPSLA90 Conference on Object Oriented Programming ACM, 1990, , pages 101--115.

....this direction has been reported 8.2 Related Work 155 in [63] A lot of effort has been done in order to give semantics for object oriented languages. Most of the work in this area defines semantics in terms of mathematical models based on set theory [18, 14] metric spaces [3] category theory [65, 19, 35], and hidden order sorted algebra [31, 28, 36, 35] Exceptions are [15] which defines an assertional style proof system, and [88] and [59] which give the semantics in terms of a process algebra based on operational semantics [70] By contrast, the semantics developed here is based on the simple ....

....on the efficiency of our approach and suggest modifications to the language, its semantics, and its notion of refinement. FOOPS After formally developing large applications using FOOPS, we would also be able to better compare this language with other object oriented specification languages [58, 11, 80, 65, 2, 61] and process algebras [51, 69, 5] Moreover, we could then explore the suitability and expressiveness of the mechanism for object protection, and consider whether it should be extended. Here we just considered a few examples using this mechanism. Operational Semantics The operational semantics ....

Jos'e Meseguer. A logical theory of concurrent objects. In Proceedings of ECOOP-OOPSLA90 Conference on Object Oriented Programming, pages 101--115. ACM, 1990.

....f) allows arbitrary changes and extensions of the defined sorts according to a stated signature morphism f . The semantics of Maude is based on concurrent term rewriting. We present the four rewriting rules for the unsorted case of unconditional rewrite rules. For a more detailed description, see [13]. A specification in Maude is a rewrite system R = Sigma ; E; L; T ) where Sigma = S; C; F; M) is a signature (consisting of sort names, class declarations, subsort ordering, function symbols and message names) E a set of equations, L a set of labels of rewrite rules and T a set of rewrite ....

J. Meseguer. A logical theory of concurrent objects. ACM SIGPLAN Notices, 25(10):101--115, Oct 1990.

....active objects. A recent breed of OOCP (Object Oriented Concurrent Programming) languages attempt to provide maximum computational and modeling power through concurrency of objects. Recent work has also been successful in establishing strong, theoretical foundations for concurrent objects[1, 15, 2, 12, 6]. The implementation of efficient OOCP languages, unfortunately, had not been as successful. The problem was that the overhead from message reception to dynamic method dispatching consumes a significant amount of execution time (e.g. as much as 4000 machine cycles or 500 seconds at 8 MHz clock ....

....resides in the template segment, and is pointed to by all the objects in the node. ffl The Class Specific Text: The class specific text is the portion of the object code that realizes the single thread of control of the object. the sequential 2 Some formal theory of concurrent objects, notably [12], allow for internal concurrency; in this case, an object may span multiple nodes. Whether or not this is useful in practice is the subject of future research. t request object ID create a new object and return its ID and pass the control to the object request a new object receive a new ....

Jos'e Meseguer. A logical theory of concurrent objects. In Proc. of OOPSLA/ECOOP'90, Ottawa, Canada, pages 101--115, October 1990.

....encapsulation, code re use, and application frameworks[32] and can serve as a powerful platform for parallel applications on MPPs 1 . Much work on establishing useful concurrent OO language models have been quite fruitful: they include Actors[1] POOL[3, 4] Hybrid[20, 21] ABCL[34] and Maude[17]. Despite such background, plus promising results in impressive pioneering research systems such as POOL DOOM[6] we do acknowledge that concurrent OO languages have not yet seen widespread use in practice. We believe that the two major impediments are as follows: Myth that Real (Parallel) ....

....because the basic operations require first class operations on the visible set which dictates the acceptset of an object per each method invocation. Meseguer recently proposed a solution to the inheritance anomaly problem with the Maude language[18] which is base on concurrent rewriting logic[17]. Inheritance anomaly is avoided in Maude with side conditions placed on the rewrite rules of the logic serving as guards, avoiding the state partitioning anomaly. In addition, rewrite rules in Maude can operate on the term structures themselves as first class values, providing implicit reflective ....

Jos'e Meseguer. A logical theory of concurrent objects. In Proceedings of OOPSLA'90, volume 25, pages 101--115. SIGPLAN Notices, ACM Press, October 1990.

....concurrent computation models [31, 29] In [14] a reflective concurrent object model is formalized and used to specify and reason about composable communication protocols. This model generalizes the actor onion skin model of [3, 18, 38, 17, 2, 37, 7] and the rewriting logic concurrent object model [26, 33, 32]. Our work on meta architectures for ODS has been motivated by various work in the areas of programming language and system design, and distributed algorithms some of which is mentioned in the previous subsection. The work described in this paper has concentrated on developing a semantic ....

Jose Meseguer. A logical theory of concurrent objects. In ECOOP-OOPSLA'90 Conference on Object-Oriented Programming, Ottawa, Canada, October 1990, pages 101--115. ACM, 1990.

....a Reliable Broadcasting Protocol in Maude Grit Denkery, J.J. Garcia Luna Acevesz, Jos e Meseguery, Peter Csaba Olveczkyy, Jyoti Rajuz, Brad Smithz, Carolyn L. Talcottq y Computer Science Laboratory, SRI International, Menlo Park, CA 94025, USA fdenker,meseguer,peterg csl.sri.com z Computer Engineering Department, University of California, Santa Cruz, CA 95064, USA fjj,jyoti,bradg cse.ucsc.edu q Computer Science Department, Stanford University, Palo Alto, CA 94305, USA clt sail.stanford.edu March 8, 1999 1 Introduction This ....

....Garcia Luna Acevesz, Jos e Meseguery, Peter Csaba Olveczkyy, Jyoti Rajuz, Brad Smithz, Carolyn L. Talcottq y Computer Science Laboratory, SRI International, Menlo Park, CA 94025, USA fdenker,meseguer,peterg csl.sri.com z Computer Engineering Department, University of California, Santa Cruz, CA 95064, USA fjj,jyoti,bradg cse.ucsc.edu q Computer Science Department, Stanford University, Palo Alto, CA 94305, USA clt sail.stanford.edu March 8, 1999 1 Introduction This paper presents a formal and executable specification of a new protocol for reliable broadcasting of information in networks ....

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Jos'e Meseguer. A logical theory of concurrent objects. In ECOOPOOPSLA '90 Conference on Object-Oriented Programming, Ottawa, Canada, October 1990, pages 101--115. ACM, 1990.

....over unbounded channels. Maude. In recent years several proposals have been made to extend abstract data type techniques in order to cover the dynamic aspects of object oriented systems, see Section 4.5.2. A prominent approach is Meseguer s Rewriting Logic as realized in the Maude language [668, 670]. In Maude the functional aspects of a concurrent object oriented system are described in the algebraic specification language OBJ, whereas the dynamic aspects are modelled by nondeterministic rewriting. A Maude case study is presented in [602] where an airport system is modelled by an abstract ....

....give a classification of inheritance relations, and a family of object composition operators are proposed in [8] intended to be a first attempt at developing a theory of modules with state. Some other work concerned with applying algebraic or logical techniques to object oriented programming is [668, 750, 3]. The entity specifications of [805] are a formalism which can be used to specify object systems. 4.4 States The extension of the usual algebraic approach to the case with state is geard towards imperative and object oriented languages, information systems, and databases. There are several ways ....

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J. Meseguer. A logical theory of concurrent objects. In N. Meyrowitz, editor, ECOOP-OOPSLA '90 Conference on Object-Oriented Programming, pages 101--115, Ottawa (Canada), Oct. 1990. ACM.

....a deriva c ao de implementa c oes. 1 Introduction A lot of effort has been done in order to define formal semantics for object oriented languages. Most of the work in this area defines semantics in terms of mathematical models based on set theory [6] metric spaces [1] category and sheaf theory [12, 3], and hidden order sorted algebra [7] Exceptions are [5] which defines an assertional style proof system, and [17] and [11] which give the semantics in terms of a process algebra based on operational semantics [13] Because of the lack of a fully abstract mathematical model for interleaving, ....

Jos'e Meseguer. A logical theory of concurrent objects. In Proceedings of ECOOP-OOPSLA90 Conference on Object Oriented Programming, pages 101--115. ACM, 1990.

.... cut is readily available in Prolog) In CPU [MN87] the user has to metaprogram the inheritance semantics. Our proposal, MU, falls under the third group of the above classification. There are solutions that do not restrict logic to mean just Horn clause logic, like FOOPlog [GM87] and Maude [Mes90], which put much emphasis on algebra (algebraic specifications, rewriting) or PRIZ [MT90] where deduction is used for synthesizing algorithms from specifications and not in execution. The list of mergers, mentioned in this section, does not pretend to be complete, but rather to illustrate the ....

J. Meseguer. A logical theory of concurrent objects. In OOPSLA ECOOP '90 Proc.: Conf. on OOP Syst., Lang. and Appl., Europ. Conf. on OOP, Ottawa, Oct 1990, pp 101-15. 1990. (SIGPLAN Notices, 20(10)).

....engine is designed with the explicit goal of being highly extensible and of supporting rapid prototyping and formal methods applications, but its semi compilation techniques allow it to meet those goals with good performance. 1 Introduction Maude is a logical language based on rewriting logic [17,24,20]. It is therefore related to other rewriting logic languages such as Cafe [10] ELAN [12] and DLO [6] The equational language OBJ [11] can be regarded as a functional sublanguage of Maude. This paper gives an introduction to the language and its interpreter implementation. Particular emphasis ....

Jos'e Meseguer. A logical theory of concurrent objects. In ECOOP-OOPSLA'90 Conference on Object-Oriented Programming, Ottawa, Canada, October 1990.

....and CASL. CafeOBJ [26, 27] is being built at the Japan Institute of Science and Technology under the direction of Prof. Kokichi Futatsugi; it extends OBJ3 with hidden algebra [55, 80, 68, 67] for behavioral specification, and with rewriting logic [113, 114] for applications programming. Maude [112, 16] is being built at SRI International under the direction of Dr. Jos e Meseguer; it extends OBJ with rewriting logic, and has been successfully used for metaprogramming, reflection, and algorithm implementation [17, 18] CASL [19] is being developed by a European consortium called CoFI, whose ....

....has logical variables. OBJ3 terms can have state in some sense, but they can only be used through built in equations. An alternative approach to object oriented programming, supporting concurrent objects and general concurrent systems programming, is being developed at SRI in the language Maude [112, 16], which uses rewriting logic [113, 114] as a basis for very direct systems modeling. Someday, we may implement FOOPlog [74] or MaudeLog, which combine the functional, logic, and object oriented paradigms. We find that it is relatively easy to build such systems on top of OBJ3, and we expect that ....

Jos'e Meseguer. A logical theory of concurrent objects. In ECOOP-OOPSLA'90 Conference on ObjectOriented Programming, Ottawa, Canada, October 1990.

....only an optional part of the righthand side, i.e. that it can be omitted in some rules so that the object is then deleted. In addition, p new objects may be created, and q new messages may be generated for p; q 0. The above representation of objects is the one adopted in the Maude language [112, 127, 116] and implicitly assumes globally unique names. Other representations are of course possible. For example, in her theory of actors and actor components, Carolyn Talcott adopts instead a more abstract representation of objects as abstract actors [153] where objects can be renamed by a form of ....

J. Meseguer. A logical theory of concurrent objects. In ECOOP-OOPSLA'90 Conference on Object-Oriented Programming, Ottawa, Canada, October

....We brie y introduce the rewriting logic model for a distributed system con guration as a soup (multiset) of concurrent objects and messages that behave according to a set of rewrite rules describing the behavior of individual objects. In particular, we specialize the rewriting logic object model [16,18,20] to the case of asynchronous message passing. We then introduce meta objects, which can be layered to form towers that appear to their environment just like concurrent objects. 2.1 Concurrent Objects in Rewriting Logic We adopt the treatment of concurrent objects by rewrite theories in [19] We ....

J. Meseguer. A logical theory of concurrent objects. In ECOOP-OOPSLA'90 Conference on Object-Oriented Programming, Ottawa, Canada, October

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Jos'e Meseguer. A logical theory of concurrent objects. In N. Meyrowitz, editor, Proceedings ECOOP-OOPSLA'90 Conference on Object-Oriented Programming, Ottawa, Canada, October

....and powerful, and that allows many advanced metaprogramming and metalanguage applications. The present paper documents Maude 1.0, and explains Maude s basic concepts in a leisurely and mostly informal style, illustrating those concepts with examples. Early language design for Maude appeared in [35, 46, 38]. A first implementation of Maude, supporting reflection, was presented and demonstrated at the First International Workshop on Rewriting Logic in September 1996 [13] 3 CHAPTER 1. INTRODUCTION 4 A beta version has been available since March 1998 [9] 1.1 The Logical Basis of Maude Maude s ....

Jos'e Meseguer. A logical theory of concurrent objects. In ECOOPOOPSLA '90 Conference on Object-Oriented Programming, Ottawa, Canada, October 1990, pages 101--115. ACM, 1990.

....2 Rewriting Semantics of Distributed Meta Objects We model a distributed system configuration as a soup (multi set) of concurrent objects and messages that behave according to a set of rewrite rules describing the behavior of individual objects. 5 We specialize the rewriting logic object model [18, 22, 26] to the case of asynchronous message passing. We call these distributed objects. We then introduce meta objects, which can be layered to form towers that appear to their environment just like distributed objects. The communication between a distributed object and its meta object is synchronous. ....

J. Meseguer. A logical theory of concurrent objects. In ECOOP-OOPSLA'90 Conference on ObjectOriented Programming, Ottawa, Canada, October 1990, pages 101--115. ACM, 1990.

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J. Meseguer. A logical theory of concurrent objects. ACM SIGPLAN Notices, 25#10#:101#115, Oct 1990. Proc. OOPSLA#ECOOP '90.

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