4.6 Discussion and Historical Remarks 81
The only steps of Stack-containers that may cause the plan’s length to be non-
optimal are the ones in the else clause at the end of the algorithm. However, these
steps usually are not executed very often because the only time they are needed is
when there is no other way to progress toward the goal.
4.6 Discussion and Historical Remarks
Although state-space search might seem like an obvious way to do planning, it
languished for many years. For a long time, no good techniques were known for
guiding the search; and without such techniques, a state-space search can search a
huge search space. During the last few years, better techniques have been developed
for guiding state-space search (see Part III of this