The GRAPHPLAN algorithm (Blum&Furst)
Basic idea: analysis of the “plan graph” can eliminate many bad choices
- iterative deepening search scheme that combines forward projection to determine feasible actions with backward regression to find valid plans
- build the plan graph forward in “stages”
- note conflicts (mutually exclusive actions, propositions) in the graph
- search backward for a solution plan
- if one is not found, extend the plan graph forward and repeat
- can (sometimes) determine a stage after which a solution will not appear