Agents Based on Propositional Logic 1 7 7

Agents Based on Propositional Logic 1

7. 7. 1 The current state of the World • Deducing what to do from a knowledge base • Knowledge base is composed of axioms • General knowledge about how the world works 2

7. 7. 1 The current state of the World • Wumpus world – Where am I, is that square safe, and so on 3

Wumpus World • • Grab Shoot Climb Four orientations 4

Wumpus World 5

Wumpus World • Fluent ? 6

Wumpus World • Fluent => 7

Wumpus World • Fluent – Time step 8

7. 7. 2 A hybrid agent • Condition-action & problem-solving algorithms. • By Asking questions of the knowledge base, to work out which squares are safe and which have yet to visited. 9

7. 7. 3 Logical state estimation • Computational expense • Belief state: if there are n fluent symbols for time t, then there are • Physical state: • Conservative approximation – Weakness? 10

7. 7. 4 Making plans by propositional inference • 謀定而後動 • The key step in using SATPLAN is the construction of the knowledge base. 11

7. 7. 4 Making plans by propositional inference • Surprises: – It can finds models with impossible actions, such as shooting with no arrow. – The creation of plans with multiple simultaneous actions which is not allowed. 12