Strategic Directions in Object-Oriented Programming

This paper has provided an overview of the field of object-oriented programming. After presenting a historical perspective and some major achievements in the field, four research directions were introduced: technologies integration, software components, distributed programming, and new paradigms. In general there is a need to continue research in traditional areas:\ud (1) as computer systems become more and more complex, there is a need to further develop the work on architecture and design; \ud (2) to support the development of complex systems, there is a need for better languages, environments, and tools; \ud (3) foundations in the form of the conceptual framework and other theories must be extended to enhance the means for modeling and formal analysis, as well as for understanding future computer systems

Process-Oriented Parallel Programming with an Application to Data-Intensive Computing

We introduce process-oriented programming as a natural extension of object-oriented programming for parallel computing. It is based on the observation that every class of an object-oriented language can be instantiated as a process, accessible via a remote pointer. The introduction of process pointers requires no syntax extension, identifies processes with programming objects, and enables processes to exchange information simply by executing remote methods. Process-oriented programming is a high-level language alternative to multithreading, MPI and many other languages, environments and tools currently used for parallel computations. It implements natural object-based parallelism using only minimal syntax extension of existing languages, such as C++ and Python, and has therefore the potential to lead to widespread adoption of parallel programming. We implemented a prototype system for running processes using C++ with MPI and used it to compute a large three-dimensional Fourier transform on a computer cluster built of commodity hardware components. Three-dimensional Fourier transform is a prototype of a data-intensive application with a complex data-access pattern. The process-oriented code is only a few hundred lines long, and attains very high data throughput by achieving massive parallelism and maximizing hardware utilization.Comment: 20 pages, 1 figur

A unified framework for verification techniques for object invariants

Object invariants define the consistency of objects. They have subtle semantics, mainly because of call-backs, multi-object invariants, and subclassing. Several verification techniques for object invariants have been proposed. It is difficult to compare these techniques, and to ascertain their soundness, because of their differences in restrictions on programs and invariants, in the use of advanced type systems (e.g., ownership types), in the meaning of invariants, and in proof obligations. We develop a unified framework for such techniques. We distil seven parameters that characterise a verification technique, and identify sufficient conditions on these parameters which guarantee soundness. We instantiate our framework with three verification techniques from the literature, and use it to assess soundness and compare expressiveness.peer-reviewe

Object-oriented programming with mixins in Ada

Recently, I wrote a paper discussing the lack of 'true' object-oriented programming language features in Ada 83, why one might desire them in Ada, and how they might be added in Ada 9X. The approach I took in this paper was to build the new object-oriented features of Ada 9X as much as possible on the basic constructs and philosophy of Ada 83. The object-oriented features proposed for Ada 9X, while different in detail, are based on the same kind of approach. Further consideration of this approach led me on a long reflection on the nature of object-oriented programming and its application to Ada. The results of this reflection, presented in this paper, show how a fairly natural object-oriented style can indeed be developed even in Ada 83. The exercise of developing this style is useful for at least three reasons: (1) it provides a useful style for programming object-oriented applications in Ada 83 until new features become available with Ada 9X; (2) it demystifies many of the mechanisms that seem to be 'magic' in most object-oriented programming languages by making them explicit; and (3) it points out areas that are and are not in need of change in Ada 83 to make object-oriented programming more natural in Ada 9X. In the next four sections I will address in turn the issues of object-oriented classes, mixins, self-reference and supertyping. The presentation is through a sequence of examples. This results in some overlap with that paper, but all the examples in the present paper are written entirely in Ada 83. I will return to considerations for Ada 9X in the last section of the paper

Component Composability Issues in Object-Oriented Programming

Building software from reusable components is considered important in reducing development costs. Object-oriented languages such as C++, Smalltalk and Java, however, are not capable of expressing certain aspects of applications in a composable way. Software engineers may experience difficulties in composing applications from components, for example if components implement code for multiple views, dynamic inheritance and synchronization [Aksit96]. If these aspects have to be programmed, then object-oriented languages may require a considerable amount of redefinition although this may not be intuitively necessary. To solve the composability problems, languages must be enhanced modularly without losing their basic characteristics. In addition, since more than one problem can be experienced for the same object, enhancements must be independent from each other. We have extended the conventional object-oriented model using the concept of composition-filters. Composition-filters can be attached to objects expressed for example in Smalltalk and Java. A number of different filter types have been defined, each addressing a certain concern. This paper first illustrates some practical problems and then introduces composition-filters solutions to overcome these problems

Object-oriented Programming Laws for Annotated Java Programs

Object-oriented programming laws have been proposed in the context of languages that are not combined with a behavioral interface specification language (BISL). The strong dependence between source-code and interface specifications may cause a number of difficulties when transforming programs. In this paper we introduce a set of programming laws for object-oriented languages like Java combined with the Java Modeling Language (JML). The set of laws deals with object-oriented features taking into account their specifications. Some laws deal only with features of the specification language. These laws constitute a set of small transformations for the development of more elaborate ones like refactorings