Practice
Traditional domain-independent planners can generate plans of only a few steps.
Prodigy, Nonlin, UCPOP, ...
Practical systems minimize or eliminate search by employing
complex search control rules, hand-tailored to the search engine and the particular search space (Sacerdoti 1975, Slaney 1996, Bacchus 1996)
pre-compiling entire state-space to a reactive finite-state machine (Agre & Chapman 1997, Williams & Nayak 1997)
Scaling remains problematic when state space is large or not well understood!