Improving design and implementation of OO container-like component libraries

Abstract

Object-oriented design is usually driven by three main reusability principles: step-by-step design, design for reuse and design with reuse. However, these principles tend to be just partially applied to the subsequent object-oriented implementation, often because they conflict with other quality criteria (remarkably, efficiency). So, there is a gap between design and implementation: due to these conflicts developers use to give up design level abstractions during the implementation. In this paper we present a framework for bridging this gap for a concrete domain, the design and implementation of object-oriented container-like component libraries, such as JCF, STL, Booch Components, LEDA, etc. At the core of the framework we propose a new design pattern called emph{Shortcut} together with its corresponding implementation. The Shortcut pattern, introduced in a generic base class container, provides a secure and efficient access to items in a container decoupled from the implementation details of concrete containers. Shortcut enhances applying the same principles that drive the design process to the implementation process of these libraries: step-by-step implementation, implementation with reuse and implementation for reuse without penalising other quality criteria. Our framework not only supports the design and implementation of new libraries but also the reengineering of existing ones to overcome some of their drawbacks. We show by a case study, reengineering the Booch Components in Ada95, the application and benefits of our framework.