Resolution_Part_3

# Resolution_Part_3 - Substitution Substitution is a finite...

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Substitution Substitution: is a finite set of pairs of terms denoted as [X 1 / t 1 , . .., X n / t n ] where each t i is a term and each X i is a variable. Every variable is mapped to a term; if not explicitly mentioned, it maps to itself. For example: date(D, M, 2001) and date(D1, may, Y1) Substitution: e= [D/D1, M/may, Y1/2001] York University- CSE 3401 15 04_Resolution

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Applying substitution to clauses Substitution of a clause is defined by applying substitution to each of its literals: e( p :- q 1 , . .., q k .) = e(p) :- e(q 1 ), . .., e(q k ). Example: C: pass_3401(X):- student(X, Y), study_hard(X). e=[X/ john, Y/ 3401] e(C)= pass_3401(john):- student(john, 3401), study_hard(john). York University- CSE 3401 16 04_Resolution
Applying substitution to literals Example: p(X, f(X, 2, Z), 5) e= [X/5 , Z/h(a,2+X)] e(p(X, f(X, 2, Z), 5))= p(5, f(5, 2, h(a, 2+X)), 5) Note: Simultaneous substitution X in h(a,2+X) is not substituted Example: r(X, Y)

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Resolution_Part_3 - Substitution Substitution is a finite...

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