Fundamental Programming Concepts Research Articles

Object-Oriented Programming in Modern Fortran

Fundamental concepts of object-oriented programming (OOP) are considered, including abstract data types, encapsulation, inheritance, and static and dynamic polymorphism. Constructs of Fortran 90/95 that support the greater part of those concepts are discussed.

Methods and Tools of Component Programming

The mainstreams of development of programming and automatic programming tools under the guidance of E. L. Yushchenko are considered. Fundamental concepts of component programming are defined such as a component, a component model, a framework, a method of integration of components, testing, and deployment.

Dragoon: an object-oriented notation supporting the reuse and distribution of Ada software

Among the more radical proposals for changes to the Ada standard in Ada9X are those advocating the introduction of "object-oriented" features exemplified by languages such as Smalltalk and Eiffel. DRAGOON is a language which supports the fundamental concepts of object-oriented programming in an Ada style, while retaining most of the features of current Ada. In other words it supports "Ada-oriented" object-oriented programming. It also employs enhanced forms of multiple inheritance to support concurrency and distribution. Therefore, although not designed specifically as a proposal for the Ada9X project, DRAGOON may serve as a basis for the development of Ada in an "object-oriented" direction. This paper provides a brief overview of the language.

Pragmatic problems with step-wise refinement program development

This paper presents a generalization of two fundamental programming concepts, LOCAL ABSTRACTIONS and GLOBAL ABSTRACTIONS, and a survey of several mechanisms for implementing them. Global abstractions are semantic definitions (of objects) used throughout a program, whereas Local abstractions are refinement steps generated by the subdivision of a problem into subproblems. Global abstractions are very well supported in today's programming languages, but there is no mechanism entirely satisfactory for the "natural" development of programs using top-down step-wise decomposition techniques. Current languages lack means of expressing the hierarchical tree structure of programs. The structure of the program <u>must be retained explicitly</u>, and with varying degrees of detail at different levels corresponding to the way the program was developed. There is an important deficiency in the process of refining the solution to a problem: local abstractions, which describe intermediate stages of the solution, are replaced by their corresponding refinements.In particular, we discuss some inadequacies of "the facto" structuring constructs in modern languages, showing that, for instance, procedures should not be used for represeting refinements, since these are intended to control the "static" program structure (refinements may well represent non-executable pieces of code!). Finally, we propose the introduction of two new DESIGN constructs for developing structured programs which can show and maintain the solutions's structure as produced during the development process.

Pragmatic problems with step-wise refinement program development

This paper presents a generalization of two fundamental programming concepts, LOCAL ABSTRACTIONS and GLOBAL ABSTRACTIONS, and a survey of several mechanisms for implementing them. Global abstractions are semantic definitions (of objects) used throughout a program, whereas Local abstractions are refinement steps generated by the subdivision of a problem into subproblems. Global abstractions are very well supported in today's programming languages, but there is no mechanism entirely satisfactory for the "natural" development of programs using top-down step-wise decomposition techniques. Current languages lack means of expressing the hierarchical tree structure of programs. The structure of the program <u>must be retained explicitly</u>, and with varying degrees of detail at different levels corresponding to the way the program was developed. There is an important deficiency in the process of refining the solution to a problem: local abstractions, which describe intermediate stages of the solution, are replaced by their corresponding refinements.In particular, we discuss some inadequacies of "the facto" structuring constructs in modern languages, showing that, for instance, procedures should not be used for represeting refinements, since these are intended to control the "static" program structure (refinements may well represent non-executable pieces of code!). Finally, we propose the introduction of two new DESIGN constructs for developing structured programs which can show and maintain the solutions's structure as produced during the development process.

Duality in Markov Decision Problems with Countable Action and State Spaces

The recent literature contains several papers which explore mathematical programming formulations of particular Markov sequential decision problems. Each of these papers deals with finite state and action spaces; thus, the corresponding programming formulations yield dual finite linear programs. In this paper these investigations are extended to include countable action and/or state spaces for finite horison problems. Of particular interest are the duality aspects of the mathematical programming formulations. In addition, employing conditions analogous to fundamental concepts of Haar semi-infinite dual programming, we provide sufficient conditions for the existence of optimal rules for countable action spaces. Guided by the semi-infinite duality theory we explore mathematical programming formulations for two cases: 1) Countable action space and finite state space—the result is a pair of dual semi-infinite programs; and 2) Finite action space and countable state space—we obtain a pair of infinite programs. In the latter case we show that no duality gap occurs and obtain duality results comparable to those of finite linear programming.