As a side comment, my partner and I feel like this problem set is almost
like the last one (maybe even worse) because to ensure the correct
parsing of a limited set of sentences, we have to perform the same sort
of changes to the grammar as we did in the past problem set. For
example, we don't want "what movies are playing at titanic" to be
parsed. We have to have very specific rules to limit the types of
parsings possible.
You should not get into doing this kind of thing by detailed changes
in the grammar rules. What you are trying to capture are semantic
relationships which should be captured in a general way. We'll talk
more about this on Tuesday.
For now, add vocabulary to cover the class of sentences you are
interested in and simply point out what you see as the general
limitations in the grammar and semantics and don't get into detailed
hand-drafting of rules to block semantically ill-formed sentences.
Tomas