Abstract
A complex large scale system is a central subject of systems engineering. However, there is no integrated theory for it partially because it has been treated on a specialized model built for a specific problem. This paper, in order to lay a foundation for a theory of a complexlarge scale system, introduces a general definition of a complex system in the framework of the general systems theory and characterizes an interaction which is one of the most basic concepts of a complex system.
This paper shows that every interaction consists of two primitive interactions, process and system interactions and that they have some unique representations. Models of complex systems are classified according to their types of interactions and it is shown as an application of the above analysis that this classification is relative to realization of a system, that is, a model can be transformed from one type into another without changing its significance by restructuring its input output pair.
