Polyphonic C# is an extension of the C# language with new asynchronous concurrency constructs, based on the join calculus. We describe the design and implementation of the language and give examples of its use in addressing a range of concurrent programming problems.

This paper aims at classifying and discussing the various ways along which the object paradigm is used in concurrent and distributed contexts. We distinguish the library approach, the integrative approach, and the reflective approach. The library approach applies object-oriented concepts, as they are, to structure concurrent and distributed systems through class libraries. The integrative approach consists in merging concepts such as: object and activity, message passing and transaction, etc. The reflective approach integrates class libraries intimately within an object-based programming language. We discuss and illustrate each of these approaches and we point out their complementary levels and goals. Technical Report - May 1998 Laboratoire de Syst`emes d'Exploitation D'epartement d'Informatique Ecole Polytechnique F'ed'erale de Lausanne CH-1015 Lausanne, Switzerland To appear in ACM Computing Surveys, September 1998. 1 Introduction It is now well accepted that the object paradi...

We propose an object-oriented calculus with internal concurrency and class-based inheritance that is built upon the join calculus. Method calls, locks, and states are handled in a uniform manner, using asynchronous messages. Classes are partial message definitions that can be combined and transformed. We design operators for behavioral and synchronization inheritance. We also give a type system that statically enforces basic safety properties. Our model is compatible with the JoCaml implementation

. This paper presents an imperative and concurrent extension of the functional object-oriented calculus described in [FHM94]. It belongs to the family of so-called prototype-based object-oriented languages, in which objects are created from existing ones via the inheritance primitives of object extension and method override. Concurrency is introduced through the identification of objects and processes. To our knowledge, the resulting calculus is the first concurrent object calculus to be studied. We define an operational semantics for the calculus via a transition relation between configurations, which represent snapshots of the run-time system. Our static analysis includes a type inference system, which statically detects message-not-understood errors, and an effect system, which guarantees that synchronization code, specified via guards, is side-effect free. We present a subject reduction theorem, modified to account for imperative and concurrent features, and type and effect soundne...

Abstract. This paper is about formal development methods for concurrent programs. Interference is the bane of the quest for compositional methods for concurrency. Concepts from object-oriented languages are argued to be a promising way of taming interference. Two approaches to development are described which are applicable to differing degrees of interference.

Abstract-PRISWDB is a full-fledged parallel, main memory relational database management system the design of which is characterized by two main ideas. In the first place, high performance is obtained by the use of parallelism for query processing and main memory storage of the entire database. In the second place, a flexible architecture for experimenting with functionality and performance is obtained via a modular implementation of the system in an object-oriented programming language. This paper describes the design and implementation of PRISWDB in detail. Also, a performance evaluation of the system shows that the system is comparable to other state-of-the-art database machines. The prototype implementation of the system is ready, and runs on a 100-node parallel multiprocessor. The achieved flexibility of the system makes it a valuable platform for research in various directions. Index Terms-Parallel, main memory, relational database man-agement system, design and implementation, architecture, query execution, experimentation, integrity constraints. I.

We describe Hal, a high-level, actor-based language which has served as a test-bed for experimenting with powerful linguistic constructs for parallel and distributed programming. Hal is an architecture independent, concurrent object-oriented language which supports inheritance, synchronization constraints, continuation capture, synchronous and asynchronous message passing, and reflection. The Hal compiler has been used to execute actor programs on a number of shared and distributed memory machines. Hal allows powerful abstractions to be defined and reused. Furthermore, Hal supports the use of synchronization constraints at a fine-grained level and the use of software pipelining. In this paper, we describe the design of Hal, using specific examples to illustrate its features. We then discuss some of the implementation issues in the run-time system.

pSather is a parallel extension of the existing object-oriented language Sather. It offers a shared-memory programming model which integrates both control- and dataparallel extensions. This integration increases the flexibility of the language to express different algorithms and data structures, especially on distributed-memory machines (e.g. CM-5). This report describes our design objectives and the programming language pSather in detail. ICSI and Eidgenossische Technische Hochschule (ETH), Zurich, Switzerland. E-mail: murer@icsi.berkeley.edu. y ICSI and Computer Science Division, U.C. Berkeley. E-mail: jfeldman@icsi.berkeley.edu. z ICSI and Computer Science Division, U.C. Berkeley. E-mail: clim@icsi.berkeley.edu. x ICSI E-mail: mseidel@icsi.berkeley.edu. ii Contents 1 Introduction 4 1.1 Roadmap of this Report : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5 1.2 Grammar Notation : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 6 2...

This paper evaluates the performance of the parallel, main-memory DBMS, PRISMA/DB. First, an abstract architecture for parallel query execution is presented. A performance model for the execution of simple relational operations on this architecture is developed. The parameters in the model are set using experiments on PRISMA/DB and the performance of PRISMA/DB is analized in the context of the model. Several conclusions can be drawn from the model combined with the results of the performance experiments. Firstly, the performance of PRISMA/DB appears to be competitive with respect to other systems. Secondly, the developed model can explain the results from the performance experiments to a large extent. Also, it is concluded that observed linear speedup for small numbers of processors cannot always be extrapolated to larger numbers of processors. Finally, it is concluded that the optimal number of processors for the parallel execution of an operation is smaller for a mainmemory system than for a disk-based system. The results of this study can be used to design data fragmentation strategies for large parallel machines. ‘The work reported in this paper was conducted as part of the PRISM.4 project, a joint effort with Philips Research Laboratories Eindhoven, partially supported by the Dutch “Stimuleringsprojectteam

This paper traces the important steps in the history --up to around 1990-- of research on reasoning about programs. The main focus is on sequential imperative programs but some comments are made on concurrency. Initially, researchers focussed on ways of verifying that a program satisfies its specification (or that two programs were equivalent). Over time it became clear that post facto verification is only practical for small programs and attention turned to verification methods which support the development of programs; for larger programs it is necessary to exploit a notation of compositionality. Coping with concurrent algorithms is much more challenging -- this and other extensions are considered briefly. The main thesis of this paper is that the idea of reasoning about programs has been around since they were first written; the search has been to find tractable methods.