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

Stabler - Lx 185/209 2003
1. Download the file lrp-cnt.pl and modify the definition of parseOnce so that in addition to printing out
the number of steps in the search, it also prints out the number of steps in the derivation (= the number of
nodes in the tree).
2. Which 6 word sentence requires the longest search with this ES grammar? Put your example in at the end
of the file.
3. Add 1 or 2 rules to the grammar (don’t change the parser) in order to produce an even longer search on a
6 word sentence – as long as you can make it (but not infinite = no empty categories). Put your example at
the end of the file, and turn in the results of all these steps.
6.6.6 Additional Exercise (for those who read the shaded blocks)
(61) Gibson (1998) proposes
For initial purposes, a syntactic theory with a minimal number of syntactic categories, such as
Head-driven Phrase Structure Grammar (Pollard and Sag, 1994) or Lexical Functional Grammar
(Bresnan, 1982), will be assumed. [Note: The SPLT is also compatible with grammars assuming a
range of functional categories such as Infl, Agr, Tense, etc. (e.g. Chomsky 1995) under the assumption
that memory cost indexes predicted chains rather than predicted categories, where a chain is a set
of categories coindexed through movement (Chomsky 1981).] Under these theories, the minimal
number of syntactic head categories in a sentence is two: a head noun for the subject and a
head verb for the predicate. If words are encountered that necessitate other syntactic heads
to form a grammatical sentence, then these categories are also predicted, and an additional
memory load is incurred. For example, at the point of processing the second occurrence of
the word “the” in the object-extracted RC example,
1a. The reporter who the senator attacked admitted his error,
Det
the
NP
Noun
reporter
NP
Comp
thati
Det
the
S’
NP
S
Noun
senator
S
V
admitted
Verb
attacked
VP
VP
NP
ei
Det
the
NP
Noun
there are four obligatory syntactic predictions: 1) a verb for the matrix clause, 2) a verb for
the embedded clause, 3) a subject noun for the embedded clause, and an empty category NP
for the wh-pronoun “who.”
Is the proposed model a glc parser? If not, is the proposal a cogent one, one that conforms to the
behavior of a parsing model that could possibly work?
(62) References. Basic parsing methods are often introduced in texts about building compilers for programming
languages, like Aho, Sethi, and Ullman (1985). More comprehensive treatments can be found in
Aho and Ullman (1972), and in Sikkel (1997).
102
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