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## Next Steps

is simple enough so that it is almost a conventional situation calculus problem. Even requires more.

1. , the first game of Lemmings Jr. has 10 lemmings. We must introduce an object for the group of them, and then separate out the lemming designated to be the digger.
2. When the hole is shallow, lemmings pass over it. When it gets deep the fall in. They continue to alternate directions while in the hole, and the direction a lemming has when it falls out of the hole determines which way it will walk on the floor of .
3. Even in , the sentences about the future are derived by nonmonotonic reasoning. We haven't said how this is done. The simplest aspect of this is that the geometric relations of the chambers tend to persist, but the positions of the lemmings don't.
4. Continued events like digging or falling need both macroscopic and microscopic formalizations. At a macroscopic level, a lemming falls to the floor or digs to the ceiling of the lower chamber or walks to the end of the chamber. At a microscopic level the falling or digging is continuous and can be interrupted or can cause other events part way.
5. The geography involves describing the scene to the extent needed as as collection of related instances of spatial types. The formalization must tolerate elaborations like the change in the floor of a chamber caused by a basher (horizontal digger) plowing it up. When an elaboration is not required, it shouldn't affect the statements that are made or the reasoning done with them.
6. Concurrent action needs to be describable in whatever level of detail is needed to draw the required conclusions.
7. What a person learns and can communicate to another person is often that in a certain kind of situation certain changes can be achieved. Therefore, to be able to give advice to a Lemmings program will require a formalization of can. Something is known about this problem, less about how to formalize how something that can be done is to be accomplished.

Next: Remarks Up: Some Formulas for a Previous: Some Formulas for a

John McCarthy
Mon Mar 2 16:21:50 PDT 1998