قسمتی از متن انگلیسی
One consequence of Proposition 4.3 is thatForeward-searchis complete. An-other consequence is thatForeward-search’s search space is usually muchlarger than it needs to be. There are various ways to reduce the size of thesearch space, by modifying the algorithm toprunebranches of the searchspace (i.e., cut offsearch below these branches). A pruning technique issafeif it is guaranteed not to prune every solution; in this case the modifiedplanning algorithm will still be complete. If we have some notion of planoptimality, then pruning technique isstrongly safeif there is at least oneoptimal solution that it doesn#prune. In this case, at least one trace of themodified planning algorithm will lead to an optimal solution if one exists.Here is an example of a strongly safe pruning technique. Suppose thealgorithm generates plansπ1andπ2along two different paths of the searchspace, and supposeπ1andπ2produce the same state of the worlds. Ifπ1can be extended to form some solutionπ1π3, thenπ2π3is also a solution,and vice versa. Thus we can prune one ofπ1andπ2, and we will still beguaranteed of finding a solution if one exists. Furthermore, if the plan thatwe prune is whichever ofπ1andπ2is longer, then we will still be guaranteedof finding a shortest-length solution if one exists
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