## Problem Set 4

Assigned: Apr. 16
Due: Apr. 30.

Consider a variant of the "register" microworld, called the "buffer" world. A buffer can hold up to a fixed number of elements. For this problem, we will use buffers of size 2.

The buffer world is characterized by four fluents:

• "in(X,B)" means that element X is in buffer B.
• "empty(B)" means that buffer B is empty.
• "one(B)" means that buffer B has one element.
• "full(B)" means that buffer B is full.
There cannot be two copies of an element in the same buffer.

Conceptually there are two actions:

• You can copy an element X from buffer B1 to buffer B2.
• You can flush element X from buffer B
In order for X to be copied into buffer B2, there must be room in B2 (that is, you cannot simply overwrite another element.)

### Problem 1:

Characterize this world in the STRIPS representation. You will have to break the above actions into special cases.

### Problem 2:

Show how the POP planner can solve the following problem:
Starting situation: X and Z are in B1, Y and Z are in B2, B3 is empty.
Goal: Y is in B1, X is in B2, Y is in B3

### Problem 3:

Show how the microworld can be axiomatized in the propositional logic, giving _one_ instance of each axiom needed.