Researcher: OLe Lehrmann Madsen (Denmark)

Presented by:Rana Abdul Qadir ES-62Anas Ahmed Qureshi ES-12

Open Issues In OOP

Open issues..?

Issues on which there is no consensus in the object-oriented programming community.

There is also a difference in what is considered open in the research community and what is considered open among practitioners.

Following issues are discussed in this paper:

I. Modeling versus reuseII. Explicit conceptual frameworkIII. Class-based versus prototype-based languagesIV. Abstraction mechanismsV. Concurrency

Modeling versus reuse During the last 10 years a change of focus seems to have happened in the object-oriented community. From being mainly interested in reuse of code, the focus has shifted to analysis and design. We argue that there should be a balance between these extremes to fully realize the benefits of the potential for object-orientation to integrate analysis, design and implementation.

Explicit conceptual frameworkThe conceptual framework underlying object-oriented modeling should be formulated independently of the languages. This separation is necessary to avoid limiting the developer by the (current) expressive power of the languages and to produce new requirements for language design.

Class-based versus prototype-based languages Prototype-based languages are one of the most interesting developments within object-orientation. Prototype-based languages make it possible to program without classes, but they do in general not support programming using a class-like style. We argue that the class-like style should be supported and that it would be desirable to unify the two approaches.

Abstraction mechanismsAlthough there is some agreement about the core abstraction mechanisms, there are still a number of differences between the common languages. We discuss alternative mechanisms for supporting classification and composition, single and multiple inheritance, inner versus super, genericity versus virtual classes, encapsulation, dynamic versus static typing, contra variance versus covariance, and types versus classes.

Concurrency Simula includes a notion of quasi-parallel processes in the form of active objects that are used for representing concurrent processes. They have also been the basis for the design of concurrency in BETA. No other object-oriented language seem to have adapted the Simula notion of active object. There are a number of proposals for concurrency in object-oriented languages, but no single model has been widely accepted. We argue that the Simula approach is (still) considered a good approach to concurrency.

There are a number of issues that have not been covered in this paper, examples are: Multi-methods Class versus module Exceptions Reflections Multiparadigm languages

Thank you for Patience