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Solution to part (a)

Give a top down derivation (including all substitutions) for one answer to the query:
? adj(b,Y,c(a,c(b,c(b,c(a,emp))))).

Here is a top-down derivation:

yes(Y) <- adj(b,Y,c(a,c(b,c(b,c(a,emp))))).
  choose clause 3, with {A/b,B/Y,L/c(a,c(b,c(b,c(a,emp)))),F/F1,E/E1}
yes(Y) <- ap(F1,c(b,c(Y,E1)),c(a,c(b,c(b,c(a,emp)))))
  choose clause 2, under
yes(Y) <- ap(T2,c(b,c(Y,E1)),c(b,c(b,c(a,emp))))
  *** choose clause 1 under {T2/emp,Y/b,E1/c(b,c(a,emp))}
yes(b) <-

Computational Intelligence online material, ©David Poole, Alan Mackworth and Randy Goebel, 1998

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