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The history of database research over the past 30 years is one of exceptional productivity

that has led to the database system becoming arguably the most important development

in the field of software engineering. The database is now the underlying framework of

the information system, and has fundamentally changed the way many organizations

operate. In particular, the developments in this technology over the last few years have

produced systems that are more powerful and more intuitive to use. This has resulted in

database systems becoming increasingly available to a wider variety of users. Unfortunately,

the apparent simplicity of these systems has led to users creating databases and

applications without the necessary knowledge to produce an effective and efficient system.

And so the ‘software crisis’ or, as it is sometimes referred to, the ‘software depression’

continues.

The original stimulus for this book came from the authors’ work in industry, providing

consultancy on database design for new software systems or, as often as not, resolving

inadequacies with existing systems. Added to this, the authors’ move to academia brought

similar problems from different users – students. The objectives of this book, therefore, are

to provide a textbook that introduces the theory behind databases as clearly as possible

and, in particular, to provide a methodology for database design that can be used by both

technical and non-technical readers.

The methodology presented in this book for relational Database Management Systems

(DBMSs) – the predominant system for business applications at present – has been tried

and tested over the years in both industrial and academic environments. It consists of three

main phases: conceptual, logical, and physical database design. The first phase starts with

the production of a conceptual data model that is independent of all physical considerations.

This model is then refined in the second phase into a logical data model by removing

constructs that cannot be represented in relational systems. In the third phase, the

logical data model is translated into a physical design for the target DBMS. The physical

design phase considers the storage structures and access methods required for efficient and

secure access to the database on secondary storage.

The methodology in each phase is presented as a series of steps. For the inexperienced

designer, it is expected that the steps will be followed in the order described, and

guidelines are provided throughout to help with this process. For the experienced designer,

the methodology can be less prescriptive, acting more as a framework or checklist. To help

the reader use the methodology and understand the important issues, the methodology has

been described using a realistic worked example, based on an integrated case study,

DreamHome. In addition, three additional case studies are provided in Appendix B to

allow readers to try out the methodology for themselves.

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