SHRDLU

SHRDLU was a computer program developed by Terry Winograd that was able to understand basic commands allowing the user to move objects like blocks, cones, or balls on a computer screen.

Wikipedia includes an example conversation with SHRDLU:

Person: Pick up a big red block.
Computer: OK.
Person: Grasp the pyramid.
Computer: I DON’T UNDERSTAND WHICH PYRAMID YOU MEAN.
Person (changing their mind): Find a block which is taller than the one you are holding and put it into the box.
Computer: BY “IT”, I ASSUME YOU MEAN THE BLOCK WHICH IS TALLER THAN THE ONE I AM HOLDING.
Computer: OK.
Person: What does the box contain?
Computer: THE BLUE PYRAMID AND THE BLUE BLOCK.
Person: What is the pyramid supported by?
Computer: THE BOX.
Person: How many blocks are not in the box?
Computer: FOUR OF THEM.
Person: Is at least one of them narrower than the one which i told you to pick up?
Computer: YES, THE RED CUBE.
Person: Is it supported?
Computer: YES, BY THE TABLE.
Person: Can the table pick up blocks?
Computer: NO.
Person: Can a pyramid be supported by a block?
Computer: YES.
Person: Can a pyramid support a pyramid?
Computer: I DON’T KNOW.
Person: Stack up two pyramids.
Computer: I CAN’T.
Person: Will you please stack up both of the red blocks and either a green cube or a pyramid?
Computer: OK.
Person: Which cube is sitting on the table?
Computer: THE LARGE GREEN ONE WHICH SUPPORTS THE RED PYRAMID.
Person: Is there a large block behind a pyramid?
Computer: YES, THREE OF THEM: A LARGE RED ONE, A LARGE GREEN CUBE, AND THE BLUE ONE.
Person: Put a small one onto the green cube which supports a pyramid.
Computer: OK.
Person: Put the littlest pyramid on top of it.
Computer: OK.
Person: Does the shortest thing the tallest pyramid’s support supports support anything green?
Computer: YES, THE GREEN PYRAMID.
Person: What color is it?
Computer: BY “IT”, I ASSUME YOU MEAN THE SHORTEST THING THE TALLEST PYRAMID’S SUPPORT SUPPORTS.
Computer: RED
Person: How many things are on top of green cubes?
Computer: I’M NOT SURE WHAT YOU MEAN BY “ON TOP OF “IN THE PHRASE “ON TOP OF GREEN CUBES ” .
DO YOU MEAN:
1 – DIRECTLY ON THE SURFACE
2 – ANWHERE ON TOP OF ?
Person: 2
Computer: THREE OF THEM.
Person: Had you touched any pyramid before you put the green one on the little cube?
Computer: YES, THE GREEN ONE.
Person: When did you pick it up?
Computer: WHILE I WAS STACKING UP THE RED CUBE, A LARGE RED BLOCK AND A LARGE GREEN CUBE.
Person: Why?
Computer: TO GET RID OF IT.
Person: Why did you do that?
Computer: TO CLEAN OFF THE RED CUBE.
Person: Why did you clear off that cube?
Computer: TO PUT IT ON A LARGE GREEN CUBE.
Person: Why did you do that?
Computer: TO STACK UP THE RED CUBE , A LARGE RED BLOCK AND A LARGE GREEN CUBE.
Person: Why did you do that?
Computer: BECAUSE YOU ASKED ME TO.
Person: How did you do it?
Computer: BY PUTTING A LARGE RED BLOCK ON THE TABLE ; THEN LETTING GO OF IT ; THEN PUTTING A LARGE GREEN CUBE ON IT ; THEN LETTING GO OF THAT CUBE ; THEN PUTTING THE RED CUBE ON THAT CUBE; THEN LETTING GO OF THAT CUBE.
Person: How many objects did you touch while you were doing it?
Computer: FOUR OF THEM.
Person: What did the red cube support before you started to clean it off?
Computer: THE GREEN PYRAMID.
Person: There were five blocks to the left of the box then.
Computer: NO, ONLY FOUR OF THEM: THE RED CUBE, TWO LARGE GREEN CUBES AND A LARGE RED BLOCK.
Person: Put the blue pyramid on the block in the box.
Computer: OK.
Person: Is there anything which is bigger than every pyramid but is not as wide as the thing that supports it?
Computer: YES, THE BLUE BLOCK.
Person: Does a steeple
Computer (interrupting): SORRY, I DON’T KNOW THE WORD “STEEPLE”.
Person: A “steeple” is a stack which contains two green cubes and a pyramid.
Computer: I UNDERSTAND.
Person: Are there any steeples now?
Computer: NO.
Person: Build one.
Computer: OK.
Person: Call the biggest block “superblock”.
Computer: OK.
Person: Have you picked superblock up since we began?
Computer: YES.
Person: Why did you drop it?
Computer: BY “IT”, I ASSUME YOU MEAN THE SUPERBLOCK.
I CAN’T EXPLAIN A NON-EXISTENT EVENT.
Person: Is there anything to the right of the red pyramid?
Computer: YES, FOUR THINGS: THE BOX , THE RED CUBE, THE BLUE PYRAMID AND THE BLOCK NAMED SUPERBLOCK
Person: Thank you.
Computer: YOU’RE WELCOME!