Network structures form the basis of several classes of operations research and management science problems, and aid in the comprehension of problem structure by highlighting precedence relationships visually. For some network structures, the default layout generated by the NETDRAW procedure may result in unnecessarily long and convoluted arcs being drawn between some pairs of network nodes (see left, above). This example describes an iterative solution to this problem: using the NETDRAW and CPM procedures to generate a network layout with more straightforward arc routing (see right, above).