Though the fields of information system development, in general, and data modeling in particular — the topics of this book — have amassed an impressive amount of research knowledge during the past two decades, they currently lack a global perspective and interpretation. In this context we define information systems development as the application of information technologies (computers and telecommunications) to solve and address problems in managing and coordinating modern organizations. Data modeling is concerned with describing, organizing and analyzing the properties of the ‘rawware’ of information systems — data. A wealth of research in these fields has produced an astonishing array of empirical results and practical insights, conceptual and terminological diversity and confusion, and a large suite of tools and methods. But as many researchers and practioners alike feel, these form an isolated, disjoint, and often contradictory amalgam of knowledge. In such a situation, the synthesis of the existing knowledge is at least as valuable as the addition of more detail in the form of further empirical results, new methods and tools, and refinements in vocabulary, etc. The need for synthesis to decrease the confusion in the area has motivated us to write this book: we seek out the principal, contradictory lines of research in information systems; describe and interpret them and their results in a way which does not deny or hide their differences, but in fact highlights the differences; and thereby hope to make these lines of research understandable.