INTRODUCTION

Chapters 4 and 5 describe a unifying framework for the structured systems development models. Such a framework is useful for several reasons:

1. (a) Many projects to provide theoretical support for systems development do not use the popular structured analysis and design models. As pointed out in Davis (1982) and Martin (1983, 1984), practitioners are rather hesitant to use new tools that involve an unfamiliar formal language. On the other hand, a unifying theoretical framework that adds formal components to the notations of structured specifications permits users to continue using existing popular practices.

2. (b) Different structured models are suitable for different situations, depending on the characteristics of user requirements, the emphasis and the stage of development (Colter 1982, Lauber 1982, Sanden 1989, Shigo et al. 1980). In other words, we may need more than one of these tools during the development process of a single system. If we provide systems developers with a means of mapping from one model to another, the efficiency of systems development may be greatly improved.

3. (c) A number of development aids have been designed for individual structured models (Delisle et al. 1982, DeMarco and Soceneantu 1984, Kampen 1982, Tse 1985, Tse and Pong 1989). However, these aids are useful only for individual models, and are not applicable to others. If a mapping can be found to transform one model to another, a development aid for one structured methodology may be applied to another.

4. […]