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is simple enough so that it is almost a conventional situation
calculus problem. Even requires more.
- , 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.
- 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 .
- 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.
- 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.
- 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.
- Concurrent action needs to be describable in whatever
level of detail is needed to draw the required
conclusions.
- 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
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John McCarthy
Mon Mar 2 16:21:50 PDT 1998