Notes on computational linguistics.pdf - UCLA Department of ...
Notes on computational linguistics.pdf - UCLA Department of ...
Notes on computational linguistics.pdf - UCLA Department of ...
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Stabler - Lx 185/209 2003<br />
7.1.3 CKY example 2<br />
Since we can now recognize the language <strong>of</strong> any c<strong>on</strong>text free grammar, we can take grammars written by any<strong>on</strong>e<br />
else and try them out. For example, we can take the grammar defined by the Penn Treebank and try to parse<br />
with it. For example, in the file wsj_0005.mrg we find the following 3 trees:<br />
NNP<br />
J.P.<br />
NP<br />
NNP<br />
Bolduc<br />
,<br />
,<br />
NN<br />
vice<br />
NP-SBJ<br />
PRP<br />
He<br />
NP<br />
NP-SBJ-10<br />
NN<br />
chairman<br />
VBZ<br />
NNP<br />
W.R.<br />
succeeds<br />
NNP<br />
Terrence<br />
NP<br />
IN<br />
<strong>of</strong><br />
NNP<br />
Grace<br />
NP<br />
NNP<br />
D.<br />
NNP<br />
W.R.<br />
NP<br />
CC<br />
&<br />
NNP<br />
PP<br />
Daniels<br />
NP-SBJ<br />
NNP<br />
Grace<br />
NNP<br />
Co.<br />
S<br />
,<br />
,<br />
,<br />
,<br />
VP<br />
,<br />
,<br />
NP<br />
ADVP<br />
RB<br />
formerly<br />
VBZ<br />
holds<br />
S<br />
S<br />
WHNP-10<br />
WDT<br />
which<br />
DT<br />
a<br />
NP<br />
CD<br />
VP<br />
three<br />
NNP<br />
Grace<br />
NNP<br />
W.R.<br />
IN<br />
<strong>of</strong><br />
VBD<br />
was<br />
SBAR<br />
NP-SBJ<br />
-NONE-<br />
*T*-10<br />
NP<br />
VP<br />
VBN<br />
elected<br />
NP<br />
NP<br />
NNP<br />
Grace<br />
NP<br />
NNP<br />
Energy<br />
S<br />
VBZ<br />
holds<br />
DT<br />
.<br />
.<br />
a<br />
PP<br />
CD<br />
83.4<br />
NN<br />
vice<br />
VP<br />
NP-SBJ<br />
-NONE-<br />
*-10<br />
ADJP<br />
NP<br />
NN<br />
%<br />
.<br />
.<br />
VP<br />
S<br />
DT<br />
a<br />
NP-PRD<br />
NN<br />
interest<br />
NN<br />
chairman<br />
,<br />
,<br />
NN<br />
director<br />
NP<br />
IN<br />
in<br />
WHNP-11<br />
WP<br />
who<br />
DT<br />
this<br />
SBAR<br />
NP-SBJ<br />
-NONE-<br />
*T*-11<br />
PP-LOC<br />
JJ<br />
NP<br />
energy-services<br />
Notice that these trees indicate movement relati<strong>on</strong>s, with co-indexed traces. If we ignore the movement relati<strong>on</strong>s<br />
and just treat the traces as empty, though, we have a CFG – <strong>on</strong>e that will accept all the strings that are<br />
parsed in the treebank plus some others as well.<br />
We will study how to parse movements later, but for the moment, let’s collect the (overgenerating) c<strong>on</strong>text<br />
free rules from these trees. Dividing the lexical rules from the others, and showing how many times each rule<br />
is used, we have first:<br />
1 (’SBAR’:˜[’WHNP-11’,’S’]).<br />
.<br />
.<br />
107<br />
POS<br />
’s<br />
CD<br />
NP<br />
seven<br />
NN<br />
board<br />
NNS<br />
seats<br />
S<br />
VP<br />
VBD<br />
resigned<br />
NN<br />
company
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