Sacerdoti, E. D. (1975). The nonlinear nature of plans. STANFORD RESEARCH INST MENLO PARK CA.
We usually think of plans as linear sequences of actions. This is because plans are usually executed one step at a time. But plans themselves are not constrained by physical limitations of linearity. This paper describes a new information structure, called the procedural net, that represents a plan as a partial ordering of action with respect to time.