Logic for AI

Question 1

atomic sentences

Answer 1

represented by Capitalized strings, allowing subscripts

Question 2

knowledge base

Answer 2

a collection of sentences that the agent knows are true in a formal language

Question 3

What is the KB typically initialized with?

Answer 3

sentences about the rules about the “physics” of the world

Question 4

What does the TELL operation do?

Answer 4

adds new sentences to the KB

Question 5

What does the ASK operation do?

Answer 5

determine if a sentence can be deduced from what is already in the KB

Question 6

formal language

Answer 6

has atomic variables and connectors

Question 7

possible formal languages

Answer 7

• propositional logic
• algebra

Question 8

possible world

Answer 8

an assignment of a value to every atomic variable mentioned anywhere in the KB

Question 9

model

Answer 9

an assignment of values to only the variables in some sentence alpha

Question 10

M(alpha)

Answer 10

set of all models of alpha

Question 11

real world

Answer 11

one of the models in the KB but we don’t know which one

Question 12

how can we know whether alpha is true in the real world, when there are multiple possibilities for the real world?

Answer 12

when alpha is True in all of them

Question 13

entailment

Answer 13

sentence beta entails sentence alpha iff every model of beta is also a model of alpha

Question 14

what does a correct inference algorithm do?

Answer 14

says yes iff the answer really is yes

Question 15

soundness

Answer 15

we started with all the queries to which the inference algorithm says yes, and we checked each one and the answer for all of them really was yes

Question 16

completeness

Answer 16

we started with all the queries that we know the answer should be yes. then we apply inference algorithm to all of them, and every one is a yes