Notes on computational linguistics.pdf - UCLA Department of ...

Stabler - Lx 185/209 2003
children(Trace, []).
% visible(Node) iff Node is maximal or minimal, and not a proper segment
visible(Node) :- extended(Node, -), barlevel(Node, 2).
visible(Node) :- extended(Node, -), barlevel(Node, 0).
The predicate copy_phi_features, and the similar copy_psi_features are easily defined using our
earlier predicate copy_features:
phi_features([person, number, case, wh, index, th, finite]).
psi_features([person, number, case, wh, index, th, finite,
pronominal, anaphoric]).
copy_phi_features(Node0, Node) :features(Node0,
Features0), features(Node, Features),
phi_features(Phi),
copy_features(Phi, Features0, Features).
copy_psi_features(Node0, Node) :features(Node0,
Features0), features(Node, Features),
psi_features(Psi),
copy_features(Psi, Features0, Features).
(21) With these definitions, substitution cannot apply to the tree:
x(i,2,[],-)
x(d,2,[],-)
juliet
(22) The following tree, on the other hand, allows exactly one substitution:
x(i,2,[],-)
x(d,2,[],-) x(d,2,[],-)
hamlet
To avoid typing in the term that denotes this tree all the time, let’s add the axiom:
tree(1,
x(i,2,[],-)/[
x(d,2,[],-)/[],
x(d,2,[],-)/ -hamlet ]).
Then we can compute the substitution with a session like this:
| ?- tree(1,T),subtree(N,T),substitution(N,NewN,Moved,Trace),subtree(NewN,NewT),tk_tree(NewT).
N = n(root,x(i,2,[],-)/[x(d,2,[],-)/[],x(d,2,[],-)/ -(hamlet)],none),
T = x(i,2,[],-)/[x(d,2,[],-)/[],x(d,2,[],-)/ -(hamlet)],
NewN = n(root,x(i,2,[],-)/[x(d,2,[index:_A],-)/ -(hamlet),x(d,2,[index:_A],-)/[]],none),
NewT = x(i,2,[],-)/[x(d,2,[index:_A],-)/ -(hamlet),x(d,2,[index:_A],-)/[]],
Moved = n(1,x(d,2,[index:_A],-)/ -(hamlet),n(root,x(i,2,[],-)/[x(d,2,[index:_A],-)/ -(hamlet),x(d,2,[index:_A],-)/[]],none)),
Trace = n(2,x(d,2,[index:_A],-)/[],n(root,x(i,2,[],-)/[x(d,2,[index:_A],-)/ -(hamlet),x(d,2,[index:_A],-)/[]],none)) ?
yes
And the tree NewT gets displayed:
x(d,2,[index:A],-)
hamlet
x(i,2,[],-)
70
x(d,2,[index:A],-)