Discussion on the Zorn-Hypothesis on Inter-server Control Flow and Product Form Queueing Networks

The hypothesis: "If a system can be represented by a model without any inter-server control flow, the underlying problem is of type Product Form Queueing Network (PFQN), otherwise of type Non Product Form Queueing Network (NPFQN)" was raised by W. Zorn. This launches a new distinction criterion between Product Form and Non Product Form Queueing Networks on a structural level. In this paper a validation of this hypothesis is discussed with the help of different representative examples.