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

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Stabler - Lx 185/209 2003<br />

The number <strong>of</strong> structures defined by this grammar is an exp<strong>on</strong>ential functi<strong>on</strong> <strong>of</strong> the number <strong>of</strong> words.<br />

N= 1 2 3 4 5 6 7 8 9 10<br />

#trees = 2 5 14 132 469 1430 4862 16796 1053686 …<br />

b. N compounds [ N NN]<br />

n → nn<br />

This series same as for PPs, except PP1 is like a N3 compound:<br />

n 1 2 3 4 5 6 7 8 9 10<br />

#trees 1 1 2 5 14 42 132 429 1420 4862<br />

c. Coordinati<strong>on</strong> [ X XandX]<br />

NP → NP (and NP) ∗<br />

This is equivalent to the grammar:<br />

np → np and np<br />

np → np and np and np<br />

np → np and np and np and np<br />

np → np and np and np and np and np<br />

np → np and np and np and np and np and np<br />

np → np and np and np and np and np and np and np<br />

np → np and np and np and np and np and np and np and np<br />

np → np and np and np and np and np and np and np and np and np<br />

…<br />

n 1 2 3 4 5 6 7 8 9 10<br />

#trees 1 1 3 11 45 197 903 4279 20793 103049<br />

97

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