GPS did solve problems in several different domains, but was not as useful as had been hoped. Problems included:

1. Keeping a complete world state at each step takes a lot of storage. This restricted GPS to small problems.

2. The ``difference'' between the current state and the goal may not be an adequate guide to action. (Consider chess: the goal of checkmating the opponent doesn't tell how to play the opening.)

3. Accomplishing a subgoal might undo a higher-level goal. This could lead to loops.

4. We often want to achieve multiple goals simultaneously. (``Climb Mt. Everest and live to tell about it.'')

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