Karlheinz Kautz

What is Prototyping

Explains and defines prototyping in terms of its character, actors and types. Examines four aspects: its use in the software development process, its goals, horizontal and vertical and the relationship between prototype and application system. Clarifies the distinction between breadboard and prototype.

Evolutionary System Development

Prototyping is one approach existing alongside a number of others, such as the life cycle plan based on the “waterfall model”. In our discussion of the different approaches, we have highlighted the benefits to be had from using prototyping to support project work as compared with classical project management strategies. So far, though, we have confined ourselves to looking at the individual software project, without mapping out a global view of software development. This is precisely what we set out to do in the following sections.

Database-Oriented Development Systems

This chapter gives an overview of database-oriented development systems which we discuss in relation to prototype construction. We begin by clarifying the terms and concepts used, and then consider the various system components, illustrating their use by means of an example. To conclude, we undertake an assessment of the systems with respect to their suitability for prototyping.

Very High Level Languages

This chapter gives an overview of Very High Level Languages, insofar as they are of interest for the construction of functional prototypes. We consider VHLLs from two different angles, examining whether they are used to gain a better understanding of design (i.e., the construction process) or implementation (i.e., the constructed product).

Basic Elements of System Development

System development is the extension of information system development. The term information system is used to denote the interaction between people whose working and communication activities are considered from the point of view of the exchange and processing of information within an organization, together with the relevant organizational arrangements. Our interest focusses on information systems in which computers form the technical core, along with their relevant application software. When we speak of software development in the present book, we invariably mean the process of manufacturing application software for use in an information system. Developing software involves drawing up models and encoding some of them in a machine-interpretable language. Software development is embedded in system development. The introduction of new or changed software in an information system results in changes in working and communication activities.

Evolutionary Process Models

So far, we have looked at system development analytically in order to highlight the problems associated with software construction and their proposed solutions. We now go on to translate the results of this critical analysis into constructive development strategies. Here, a number of ideas have been put forward by computer scientists, all of them designed to avoid the weaknesses of traditional life cycle plans (see [FloyReisSchm89, Boehm88, BjerEhnKyng87]). We attempt to integrate these ideas into our own process model of evolutionary system development which emphasizes the conscious process of changing a user organization. Like any other model, our process model is based not only on technical and task-related considerations, but also on the personal values and views of those involved as to what software development is all about: Software developers should base their design decisions on the wishes and conceptions of the future users of an application system. Since it is impossible to completely anticipate the requirements and implications of a software system, design must focus on the modifiability and integratability of a system as well as the reusability of the parts already developed.

Prototyping in Practice

In this chapter we look at the role already being played by prototyping in industrial software practice. This involves going beyond the examples considered in Section 4.5 and combining discussion of the concepts examined so far and our own assessment of the relevant tools with practical experience in this field. The purpose of this chapter is to provide a sort of guide to the typical approaches and problems associated with prototyping. To this end, we draw not only on first-hand reports from the literature, but also on our own experience with the construction of large software systems as well as with teaching groups of students (see [BaeBudKuhlSylZue88, GrycKaut90]). Another important source was our analysis of a number of industrial software projects which we conducted in the context of a GI working group.52

Traditional Life Cycle Plans

In the literature, models serving the same purpose as our model in Chapter 2, i.e., the description of the software development process, are known as life cycle models because they relate to the development, use and “discarding” of a software product. In life cycle models, the basic elements are in most cases merely put in sequence, the cycle being degenerate in the sense that it is, ideally, run through only once in the life of a software product.

The Groups Involved in Prototyping

In the course of this book, it should have become clear that, whatever form it takes, prototyping invariably means a departure from traditional ways of thinking and working in software development. And this has — as we have repeatedly seen in the previous chapter — repercussions for the groups involved. Following the division adopted so far, we now go on to consider what the effects are on the three main groups involved in the design of prototyping processes: the developers, the users, and the management (a distinction being made in specific cases between user management and DP management).

The Tool Landscape

In Part II of our book, we consider how the construction of prototypes can be supported by tools. The tools currently in use are divided up into distinct classes. The following four chapters take a detailed look at each of these groups. The subsequent two chapters of Part II report on experience gained with prototype construction in software engineering projects conducted in industry and research. We also examine the interplay between the software development strategy, the groups affected and the tools used. Finally, we summarize the essentials of the book.