Chapter 16

Question 1

Difference between Logical programming and procedural programming?

Answer 1

Logical = specify results
Procedural = show how to get to results

Question 2

What is a proposition?

Answer 2

A logical statement that may or may not be true

Question 3

What represents a object in proposition?

Answer 3

Constants or variables

Question 4

What are the types of propositions?

Answer 4

Atomic + compound

Question 5

What does a compound term consist of?

Answer 5

Functor and order list of parameters

Question 6

Compound term in Prolog example

Answer 6

student(jon) student = functor, jon = argument

Question 7

What are the 2 forms for propositions?

Answer 7

Facts ( assumed to be true) and queries (truth to be determined.

Fact = jon is a student.
query = is jon a student?

Question 8

What is a compound proposition?

Answer 8

2+ atomic propositions

Question 9

What are the 2 quantifiers?

Answer 9

Exists (backwards E) universal (upside down A)

Question 10

Is resolution an inference principle?

Answer 10

Yes

Question 11

What is the unification process?

Answer 11

Finds values for variables in propositions such that the matching process can move forward

Question 12

What happens after instantiating a variable with a value and the matching fails?

Answer 12

Backtrack and instantiate variable with different value

Question 13

What are the 2 types of Horn caluses?

Answer 13

Headed (single atomic proposition on the left
Headless ( father(bob, jake) )

Question 14

Can all propositions be stated as Horn clauses?

Answer 14

No only most

Question 15

What is meant by “ Logic programming is nonprocedural”?

Answer 15

Dont state how the result must be computed but rather the form of the result

Question 16

What is a atom in Prolog?

Answer 16

String of letter, digits and underscores starting with lowercase

Question 17

What is a variable in Prolog?

Answer 17

same as atom but starts with Uppercase letter

Question 18

What are the 3 kinds of statements in Prolog?

Answer 18

Fact, Rule and Goal

Question 19

Example of a fact statement in prolog:

Answer 19

female(shelly) aka headless Horn clauses

Question 20

Example of atomic rule statement in prolog:

Answer 20

ancestor(mary,shelly) :- mother(mary,shelly) (headed horn clause)

Question 21

Example of universal rule statement in prolog

Answer 21

(headed horn clause)
parent(X,Y) :- mother(X,Y).
parent(X,Y) :- father(X,Y).
grandparent(X,Z) :- parent(X,Y), parent(Y,Z) === x is a grand parent of Z if X is a parent of Y and Y is a parent of Z

Question 22

How are goal used in prolog?

Answer 22

?- man(fred). aka is fred a man?
Conjunctive propositions:
?- father(X,mike). ( find all the X such that X is mikes father

Question 23

What are the 2 different inferencing approaches?

Answer 23

Bottom-up resolution aka forward chaining ( begin with facts and go to goal)
Top-down aka backward chaining ( begin at goal and go to fact ( prolog uses this))

Question 24

What happens if a goal has many sub goals?

Answer 24

Use BFS or DFS ( prolog uses dfs)
DFS = find complete proof for one before working on another

Question 25

How can you see each step of variable instantiations in prolog?

Answer 25

With *trace*

Question 26

What are the 4 events of the tracing model?

Answer 26

Call, Exit, Redo, Fail

Question 27

How do you assign an arithmetic expression to a variable in prolog?

Answer 27

A is B / 17 + C All variables on RHS must be instantiated, all on the LHS must not be instantiated

Question 28

Is Sum is Sum + Number "legal" and why?

Answer 28

No because either Sum is instantiated which would make the LHS illegal or not instantiated which would make the RHS illegal

Question 29

How does a list with a head and tail look like in prolog?

Answer 29

[H | T ]

Question 30

Why should the base case of recursion always be at the top in prolog?

Answer 30

cause prolog uses top to bottom matching,

Question 31

How do you check if X is a member of list Y in prolog?

Answer 31

member(X, Y)

Question 32

How do you add items to a list in prolog?

Answer 32

append (X,Y,Z) append X and Y to make Z append([a, b], [c, d], [a, b, c, d]) should be true

Question 33

What does the reverse proposition do in prolog?

Answer 33

reverse(X,Y) checks if Y is the reversed version of X

Question 34

What is the problem with prolog?

Answer 34

no Resolution order control (always top to bottom with facts and rules, and left to right with subgoals Closed-world assumption ( if false maybe just not enough to prove right) negation problem intrinsic limitations

Question 35

How do you stop backtracking in subgoals?

Answer 35

! valid_member(X) :- member(X, [...]), !, test(X).