The Blocks World

• The blocks world is a simple and commonly used instructional domain.
• It's pretty simple. There are blocks and the ground.
• Blocks can go on the ground, or on other blocks.
• You can manage this with a simple system of actions with preconditions and effects.
• You have primitive facts, which are used in the preconditions and effects.
• Block(b) says b is a block.
• On (b,x) says b is on x. x can be the ground.
• Clear(x) means x has no block on it. -Clear(x) means x has a block on it.
• Move(b,x,y) means move b from x to y. It looks like:
• Action(Move(b,x,y),
  Precond: On(b,x) and Clear(b) and Clear(y),
  Effect: On(b,y) and Clear(x) and -On(b,x) and -Clear(y))
• It's pretty simple, but can be used to explain interesting algorithms.
• It relates to the Tower of Hanoi problem.
• This language is used in STRIPS, a GOFAI planning system.