86 Chapter 5 Plan-Space Planning
5.2 The Search Space of Partial Plans
Generally speaking, a plan is a set of actions organized into some structure, e.g.,
a sequence. A partial plan can be defined as any subset of actions that keeps some
useful part of this structure, e.g., a subsequence for state-space planning. All plan-
ning algorithms seen up to now extend step-by-step a partial plan. However, these
were particular partial plans. Their actions are sequentially ordered. The total order
reflects the intrinsic constraints of the actions in the partial plan and the particu-
lar search strategy of the planning algorithm. The former constraints are needed;
a partial plan that is just an unstructured collection of actions would be meaning-
less because the ...