Unclear on planning graphs

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• Hi AIMA community. We re getting into planning now and while i understand most of the material in chapter 10, i don t understand how planning graphs are used
Message 1 of 1 , Apr 6, 2011
Hi AIMA community. We're getting into planning now and while i understand most of the material in chapter 10, i don't understand how planning graphs are used to extract heuristics that make searching for a plan faster

The 3rd edition mentions search goes faster with heuristics and planning graphs can be used to generate heuristic values. i see how that works from the initial state - the last goal literal appears at level 9 so the solution must be at least 9 steps away. What i don't understand is how you calculate a value from later states - if i'm at level 8 and literal A appears for the first time at level 9, it doesn't mean i'm 1 action away from it, just as being at level 10 doesn't mean i've achieved it

i'm also confused as to how to use the heuristic information. If i'm at level 1, literal A is at level 9 and i have 3 actions, the heuristic value for all 3 actions is the same isn't it? A heuristic doesn't help unless it makes one action appear lower cost than the other

i re-read that section a couple of times but i feel like i'm missing something really obvious

-baylor
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