GERT Networks with Basic Element Structures

Abstract

GERT networks which only contain STEOR nodes can easily be evaluated in principle as we have seen in chapter 2. Difficulties, however, are caused by nodes with deterministic exit and, above all, by nodes with AND entrance or with IOR entrance. In this chapter we treat GERT networks which, on one hand, contain non-STEOR nodes but which, on the other hand, are still relatively easily evaluated, and for which, as with STEOR networks, exactly one target event occurs with probability one during each project execution. It is obvious that these two requirements entail certain restrictions placed on the structure of the corresponding GERT networks. It proves to be expedient in this context to admit non-STEOR nodes only within special reducible subnetworks²⁾ the so-called basic element structures. After having evaluated these basic element structures, we obtain a STEOR network to which the MRP method treated in sections 2.2 and 2.3 may be applied.

For this chapter we refer to FIX [7]. The basic element structures defined in FIX [7] are called “pre-basic element structures” in this monograph, whereas now basic element structures have to satisfy additional conditions. The evaluation method presented in FIX [7], however, constructs basic element structures within the meaning of our definition.