System Paradigms as Reality Mappings

Abstract

In recent years considerable progress has been made in the field of establishing and verifying the theoretical foundations of modelling and simulation. This would most naturally lead the naive observer to expect that equivalent — relevant — progress has been made in the field of unequivocally establishing unique rules for model construction and criteria for evaluating the validity of models with reference to reality.

This chapter can be considered as an attempt both to unify the different concepts which are used in this field and to demistify some exaggerated expectations.

In the first place a comparison of the terminology used in some important chapters that follow in the first section of this book is presented.

Next the issue of “top-down” or “bottom-up” modelling is addressed and some problems with reference to the supposed antagonism between hypothesis verification and feature extraction will be laid to rest.

In another paragraph the question of what can be modelled shall briefly be handled from a more philosophical viewpoint.

In order that the reader would be able to evaluate the implications of what follows, the theoretical material that supports modelling in a positive sense will be reviewed as pieces of evidence, specifically for the validation problem.

Then a framework will be presented which links together the concepts and techniques of model building with concepts and techniques of experimentation and thus might be useful for further clarification of the issue of valid representation of systems.

Following this, three aspect-selection/decomposition paradigms for modelling are confronted with three prototypes of systems and their relation to the valid modelling problem is discussed. The chapter ends by a conclusion which attempts to outline the practical consequences for the model builder.