The concept of a network theory proposed in this paper provides a basis for systematically addressing questions concerning the design and operation of integrated processes. The route to a problem solution is characterised by the following steps. Modular process structuring takes place on hierarchically ordered levels by switching of components and linkage elements. The process module are switched mass-and energy-wise by means of opposing potential and current vectors. The linkage which is switched one-sidedly and is hence reaction-free is a special case. Process modelling utilises modular process structuring and assigns the structural modules to behaviour-describing modules, Process analysis examiones structural properties (stability, controllability, observability, sensitivity) and nonliner phenomena (ignition and extinction; boundary cycles; waves; chaos) of the overall process behaviour. Process design considers the layout and control of processes from holistic vantage points and aims at optimum determination of the nature, number, and switching of all the components and linkage elements of an integrated process in the light of a given production goal.