Difficulties with object-oriented frameworks

Abstract

The goal of an object-oriented framework is to provide a reusable design that supports the development of multiple related applications. In practice, frameworks are distributed as source code with little or no design documentation. This complicates both the instantiation and extension of these frameworks.

We illustrate this problem by examining the HotDraw framework, which provides 2D graphical editing capabilities in the Smalltalk environment. We used both the Smalltalk development environment tools and an existing framework design notation, Helm's contracts, to try to understand the framework. Our analysis of HotDraw using these approaches suggests that frameworks would be easier to instantiate and extend if more design and documentation effort were focused on two important framework interfaces: the interface exported to applications, and the interface exported to other frameworks. Based on this observation, we describe a set of usage dependences that are intended to improve framework interface design with respect to instantiation and extension.

This research was supported in part by the National Science Foundation under Grant Numbers CCR-9113367 and CCR-8858804 and by SRA (Tokyo Japan). The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the U.S. Government, or of SRA.