Judging by the looks of the two parties, the marriage between concurrent computation and object-oriented programminga union much desired by practitioners in such fields as telecommunications, high-performance computing, banking and operating systems- appears easy enough to arrange. This appearance, however, is deceptive: the problem is a hard one. This article points the way toward a possible solution. The precise problem examined here is restricted to: What is the smallest, smallest and most convincing extension to the method of systematic object-oriented software construction that can address the need of concurrent and distributed computinng as well as those of sequential computations? The article does not claim to discuss concurrency and distribution in a general and unbiased way

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Formal methods are necessary in achieving correct software: that is, software that can be proven to fulfil its requirements. Formal specifications are unambiguous and analysable. Building a formal model improves understanding. The modelling of nondeterminism, and its subsequent removal in formal steps, allows design and implementation decisions to be made when most suitable. Formal models are amenable to mathematical manipulation and reasoning, and facilitate rigorous testing procedures. However, formal methods are not widely used in software development. In most cases, this is because they are not suitably supported with development tools. Further, many software developers do not recognise the need for rigour. Object oriented techniques are successful in the production of large, complex software systems. The methods are based on simple mathematical models of abstraction and classification. Further, the object oriented approach offers a conceptual consistency across all stages of soft...

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This paper describes the integration of concurrency control in BALLOON, an object-oriented language that separates the concepts of type and class as well of subtyping and subclassing. Types are interface specifications enriched with concurrency control annotations. Classes are used to implement the operational functionality of types as well as concurrency control mechanisms. Types, classes and concurrency control annotations are independently reusable and derivable. The language takes advantage of this separation to solve the typical problems of the inheritance anomaly. 1

Many attempts have been made to add concurrency to C ++ , but much of the work has not exploited the power of C ++ , and often extensive compiler extensions are made. This paper shows how the object-oriented facilities of C ++ are powerful enough to encapsulate concurrency creation and control. We have developed a concurrent C ++ -based system which we call ABC ++ . We show how we can provide, with a standard compiler, almost all of the functionality offered by a new or extended language. Active objects, object distribution, selective method acceptance, and synchronous and asynchronous object interaction are supported. Concurrency control and synchronization are encapsulated at the active object level. The goal of ABC ++ is to allow its users to write concurrent programs without dealing with explicit synchronization and mutual exclusion constructs, and with as few restrictions on the use of C ++ as possible. ABC ++ can be implemented on either a shared memory ...

. A survey of concurrent object-oriented languages is presented. The survey is organized around three models: the Animation Model that describes a variety of relationships between threads and objects, an Interaction Model that classi#es the possible semantics of invocations and returns between a client object and a server object, and a Synchronization Model that shows di#erentways in which concurrentinvocations can be managed bya server.Anumber of representative languages are brie#y presented. The problem of synchronization in concurrent object-oriented languages is considered in detail including a discussion of the inheritance anomaly. A synchronization mechanism, called a behavior set , is shown to avoid this anomaly in certain cases. The implementation of behavior sets in ACT++, an actor-based concurrent programming framework implemented in C++, is described. 1 Introduction This survey of concurrent object-oriented programming languages is organized along the following ...

Abstract. Designing object models with concurrency features was a preoccupation of numerous researchers for the past two decades. UML, the standard object-oriented modeling language adopted by the OMG, does not tackle the issues of concurrency in its object model in a systematic way. In this paper we outline the position of the UML object model within the design space of concurrent object models described in [10], discuss the inconsistencies in the UML semantics and finally propose an object model, comprising features from UML and ATOM – a state-of-the-art concurrent object model. 1

Substantial research activity in the past few years concentrated on the design of languages and models for integrating concurrency and object-oriented features with the intention to enhance the potential for software reuse in the development of concurrent systems. Most of the work in the area has focused on the problem of specifying and reusing through inheritance synchronization constraints on the invocation of object methods. Currently, this is a widely recognized problem and several approaches have been proposed. More recent and far fewer research has addressed the issue of coordinating the execution of several objects and specifying and reusing coordination algorithms among objects. However, most proposals have addressed these problems in isolation. Furthermore, few languages supporting the proposed features are widely available and relatively little experience has been gained from their use. In this paper we present an active object model that aims at a more comprehensive approach...

Many attempts have been made in adding concurrency to C ++ either by extending the language or through the use of a class library. This paper reviews and analyzes some of the concurrent C ++ -based systems. We study the various approaches taken by these systems in adding concurrency to C ++ and how these approaches interact with the object-oriented paradigm. 1 Introduction Concurrency has been the subject of much research for over three decades. Traditionally, concurrency is concerned with threads of control and problems of synchronization and mutual exclusion. Object-oriented programming (OOP) languages provide a natural facility for modeling and decomposing a problem into self-contained entities called objects. An object is self-contained in the sense that it has exclusive control over its own internal state and communicates with the outside world through message passing. Thus it appears that the integration of the two paradigms of OOP and concurrent programming is promis...