What Needs to be Formalized?

Here are some of the phenomena of playing Lemmings that are shared by real time, real world problems and which are still not well treated in AI systems.

1. A person playing Lemmings is dealing with a process that runs too fast to be fully observed. No-one can follow the motion of 5 lemmings, let alone the 80 common in some levels. Actually, two lemmings is often too much if their images overlap.
2. The laws of motion of the lemming world are quantitative and are characterized by the computer program. However, the player's knowledge of them is qualitative and partial.
3. When the player looks at a lemming scene, he initially extracts into sentences only part of the information he may eventually use to make his decisions. Other information remains in the scene to be used if wanted. This illustrates the partial truth of Herbert Simon's slogan ``The world is its own best model''. The world is its own most comprehensive model but often not its own most intelligible model.
4. The player's knowledge of a particular situation is partial. Important parts of the scene are often out of sight.
5. There are usually too many lemmings in the scene for them all to be individuated in the player's mind. He has to refer to groups of lemmings--even groups whose composition changes.
6. Each Lemmings game has a its own geometry, and the scene must be appropriately parsed into regions of tactical significance, e.g. regions whose points are all accessible by walkers. Digging holes and placing blockers both change the effective division into regions.
7. Nevertheless, successful play also requires that important features of the scene be verbalized and that plans be made. Projection of the effects of carrying out plans is done in a verbal (for computers, logical) language.
8. It is possible to learn from experience and try again. Here Lemmings is easier than the real world, because the exact initial situation is repeated when ever a play is restarted. Moreover, Lemmings is deterministic. The same sequence of actions will always have the same effects.

People formulate in natural language facts about the Lemmings world. We can expect to devise formal tools of equal power. Besides facts, people tell each other lemming stratagems, both local and global. We will not try to formalize the physical skill of making several moves accurately and in quick succession. In the actual game, vigourous use of the pause facility can avoid much of the need for practicing fast reactions.