One day, Eta Oin wanders into the MIT Artificial Intelligence Laboratory, where she runs into the brilliant young computer program, SHRDLU. It happens that SHRDLU is just dying for someone to try out the newly developed human being “Dr. Tony Earrwig”. SHRDLU explains that this Earrwig is fairly intelligent in the limited domain of analyzing a conversation about a “toy world” containing blocks of various shapes, sizes, and colors-blocks which sit on a table, and which can be picked up and moved around. Eta Oin, fascinated, begins enthusiastically typing to SHRDLU. Earrwig dangles over her shoulder and provides a sort of running commentary, as promised.

Eta Oin: pick up a big red block.

SHRDLU: OK.

Dr. Tony Earrwig: SHRDLU answers “OK” when it carries out a command. In order to pick up the red block, it had to clear it off by finding a space for the green one and moving the green one away.

Eta Oin: grasp the pyramid.

SHRDLU: I DON’T UNDERSTAND WHICH PYRAMID YOU MEAN.

Dr. Tony Earrwig: There are three pyramids in the scene, and SHRDLU knows that phrases beginning with “the” are intended to refer to a specific object the speaker has in mind.