Ch. 7

1
Ch. 7 Logical Agents

• Supplemental slides for CSE 327
• Prof. Jeff Heflin

2
Goal-Based Agent
sensors
State


What the world is like now
How the world evolves

Environment
What it will be like if I do action A
What my actions do
What action I should do now
Goals

actuators
Agent
From Fig. 2.13, p. 50
3
Knowledge-Based Agent

• function KB-AGENT(percept) returns an
  action static KB, counter t0
• 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
• From Figure 7.1, p. 196

4
Grammar for Propositional Logic

• Sentence ? AtomicSentence ComplexSentence
• AtomicSentence ? True False Symbol
• Symbol ? P Q R
• ComplexSentence ? ? Sentence (Sentence ?
  Sentence) (Sentence ? Sentence)
  (Sentence ? Sentence) (Sentence ? Sentence)

From Figure 7.7, p. 205
5
Inference via Model Checking

• function TT-ENTAILS?(KB, ?) returns true or
  false symbols ? a list of the proposition
  symbols in KB and ? return TT-CHECK-ALL(KB, ?,
  symbols, )
• function TT-CHECK-ALL(KB, ?, symbols, model)
  returns true or false
• if EMPTY?(symbols) then if PL-TRUE?(KB, model)
  then return PL-TRUE?(?, model) else return
  true else do P ?FIRST(symbols) rest ?
  REST(symbols)
• return TT-CHECK-ALL(KB, ?, rest,
  EXTEND(P,true,model)) and TT-CHECK-ALL(KB, ?,
  rest, EXTEND(P,false,model))
• From Figure 7.4, p. 209

6
Wumpus World Agent

• function PL-WUMPUS-AGENT(percept) returns an
  action inputs percept, a list stench, breeze,
  glitter static KB, a knowledge base, initially
  containing rules of the Wumpus world x, y,
  orientation, the agents position visited,
  array of squares visited by agent, initially
  empty action, most recent action, initially
  null plan, an action sequence, initially
  empty
• update x, y, orientation, visited based on
  action if stench then TELL(KB, Sx,y) else
  TELL(KB, ?Sx,y)
• if breeze then TELL(KB, Bx,y) else TELL(KB,
  ?Bx,y)
• if glitter then action ? grab else if plan is
  nonempty then action ? POP(plan) else if for
  some fringe square i,j, ASK(KB, (?Pi,j ? ?Wi,j
  )) is true or
• for some fringe square i,j, ASK(KB, (Pi,j ?
  Wi,j )) is false then do
• plan ? A-GRAPH-SEARCH(ROUTE-PROBLEM(x,y,
  orientation, i,j, visited)) action ?
  POP(plan) else action ? a randomly chosen
  move return action
• From Figure 7.19, p. 226