Then it cank itsef what tod-wers shoul follaw from the KB Knowledge base=set of senten ina formal language Kn owlad ge base resolution Logic in general-models and entailmen Wumpus world Knowledge bases Outline LOGICAL AGENT domain-independent .. .. Wumpus world characterization Sensrs Breeze,Glitter,Smell Wumpus World PEAS description sent states,actions,etc. The agent must be able to: Ask(KB.MAKE-ACHION-Q r-SENT A simple knowledge-based agent e Logical agents Chapter 7 Chapter 7 1 Outline ♦ Knowledge-based agents ♦ Wumpus world ♦ Logic in general—models and entailment ♦ Propositional (Boolean) logic ♦ Equivalence, validity, satisfiability ♦ Inference rules and theorem proving – forward chaining – backward chaining – resolution Chapter 7 2 Knowledge bases Knowledge base Inference engine domain−specific content domain−independent algorithms Knowledge base = set of sentences in a formal language Declarative approach to building an agent (or other system): Tell it what it needs to know Then it can Ask itself what to do—answers should follow from the KB Agents can be viewed at the knowledge level i.e., what they know, regardless of how implemented Or at the implementation level i.e., data structures in KB and algorithms that manipulate them Chapter 7 3 A simple knowledge-based agent function KB-Agent( percept) returns an action static: KB, a knowledge base t, a counter, initially 0, indicating time Tell(KB,Make-Percept-Sentence( percept,t)) action ←Ask(KB,Make-Action-Query(t)) Tell KB ( ,Make-Action-Sentence(action,t)) t ← t + 1 return action The agent must be able to: Represent states, actions, etc. Incorporate new percepts Update internal representations of the world Deduce hidden properties of the world Deduce appropriate actions Chapter 7 4 Wumpus World PEAS description Performance measure gold +1000, death -1000 -1 per step, -10 for using the arrow Environment Squares adjacent to wumpus are smelly Squares adjacent to pit are breezy Glitter iff gold is in the same square Shooting kills wumpus if you are facing it Shooting uses up the only arrow Grabbing picks up gold if in same square Releasing drops the gold in same square Breeze Breeze Breeze Breeze Breeze Stench Stench Breeze PIT PIT PIT 1 2 3 4 1 2 3 4 START Gold Stench Actuators Left turn, Right turn, Forward, Grab, Release, Shoot Sensors Breeze, Glitter, Smell Chapter 7 5 Wumpus world characterization Observable?? Chapter 7 6