Interleaved Chaining

• You can also interleave chaining with some forward, and some backward.
• As the plans get more complex, this is the type of thing you need to do.
• Here, you might start with some forward chaining, but see the reachable state space get quite large.
• You could use some backward planning, but it might also get large before you reach the state space reachable from the forward space.
• You might then guess an intermediate state and chain from or to it in either direction.
• You might also use hierarchical search, then chain forward and backward from these states.
• Of course, this is heuristic, and you may never find a plan with this mechanism.