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

Stabler - Lx 185/209 2003
8. Define a binary predicate number_of_nodes(T,N) which will count the number N of nodes in any tree T.
So for example,
| ?- number_of_nodes(a/[b/[],c/[]],N).
N=3
Yes
Test your definition to make sure it works, and then submit it.
9. Write a grammar that generates infinitely many sentences with pronouns and reflexive pronouns in subject
and object positions, like
he praises titus and himself
himself praises titus
a. Define a predicate cc_testa that is true of all and only parse trees in which every reflexive pronoun is
c-commanded by another DP that is not a reflexive pronoun, so that
titus praises himself
is OK but
himself praises titus
is not OK. Test the definition with your grammar and tdp.
b. Define a predicate cc_testb that is true of all and only parse trees in which no pronoun is c-commanded
by another DP, so that
he praises titus
is OK but
titus praises him
is not OK. 17 Test the definition with your grammar and tdp.
10. As already mentioned on page 24, human languages frequently have various kinds of “reduplication.” The
duplication or copying of an earlier part of a string requires access to memory of a kind that CFGs cannot
provide, but tree grammars can.
Write a tree grammar for the language
{xx| x any nonempty str ing of ter minal symbols}
where the terminal symbols are only a and b. This is the language:
{aa, bb, abab, baba, aaaa, bbbb,...}.
Implement your tree grammar in Prolog, and test it by computing some examples and their yields, as we
did in the previous section for a n b n c n , before submitting the grammar.
17 Of course, what we should really do is to just block binding in the latter cases, but for the exercise, we just take the first step of
identifying the configurations where binding is impossible.
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