Resolution_Part_5

Resolution_Part_5 - Search Space (example) C0:...

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Search Space (example) York University- CSE 3401 29 C0: grandfather(X,Z) :- father(X,Y), parent(Y,Z). C1: parent(X,Y) :- father(X,Y). C2: parent(X,Y) :- mother(X,Y). C3: father(a,b):-. C4: mother(b,c):-. C5: mother(b,d):-. G0: :- grandfather(a,X). C0, [Z/X, X 0 /a] C3, [Y 0 /b] C1, [X 1 /b, Y 1 /X] Nothing to resolve with, backtrack! C2, [X 2 /b, Y 2 /X] C4, [X/c] TRUE, X=c ; (backtrack!) C5, [X/d] TRUE, X=d 0 04_Resolution
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Search Space What is the search strategy used by Prolog for searching the tree? Depth First Search or Breadth First Search York University- CSE 3401 30 Prolog uses DFS 04_Resolution
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1. Why is it ok to rename the variables every time we use a fresh copy of a clause (slide #24)? Doesn’t that change the clause?! Note that each variable X in our clause is actually bound by a universal quantifier ( X). In the last step of converting to CNF, we removed the quantifiers for simpler notation. Renaming the variable bound by a quantifier (dummy renaming) does not alter the semantics of the formula. York University- CSE 3401
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Resolution_Part_5 - Search Space (example) C0:...

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