a special class of stochastic pert networks

considering the network structure is one of the new approaches in studying stochastic pert networks (spn). in this paper, planar networks are studied as a special class of networks. two structural reducible mechanisms titled arc contraction and deletion are developed to convert any planar network to a series-parallel network structure. in series-parallel spn, the completion time distribution function can be calculated only by means of multiplication and convolution operations. for the first time, series-parallel networks are studied on the basis of the structural viewpoint. these networks belong to planar networks class. a key theorem provides capability of application of these mechanisms for non series-parallel planar networks