[Corpora] [Corpora-List] Unary phrase structure rules in the Penn Treebank

[hossein dehghan]

Hi,

In the Penn Treebank, there are the sentences which use unary phrase
structure rules.

For example in sentence: “Mr. Spoon said the plan is not an attempt to
shore up a decline in ad pages in the first nine months of 1989; Newsweek’s
ad pages totaled 1,620, a drop of 3.2% from last year, according to
Publishers Information Bureau.” whose phrase structure in the Penn Treebank
is:

(S (S (NP (NNP Mr.) (NNP Spoon)) (VP (VBD said) (SBAR (S (NP (DT the) (NN
plan)) (VP (VBZ is) (RB not) (NP (DT an) (NN attempt) (S (VP (TO to) (VP
(VB shore) (PRT (RP up)) (NP (NP (DT a) (NN decline)) (PP (IN in) (NP (NN
ad) (NNS pages))) (PP (IN in) (NP (NP (DT the) (JJ first) (CD nine) (NNS
months)) (PP (IN of) (NP (CD 1989))))))))))))))) (: ;) (S (NP (NP (NNP
Newsweek) (POS 's)) (NN ad) (NNS pages)) (VP (VBD totaled) (NP (NP (CD
1,620)) (, ,) (NP (NP (DT a) (NN drop)) (PP (IN of) (NP (CD 3.2) (NN %)))
(PP (IN from) (NP (JJ last) (NN year))))) (, ,) (PP (VBG according) (PP (TO
to) (NP (NNP Publishers) (NNP Information) (NNP Bureau)))))) (. .))

and the “(SBAR (S …” is a unary rule (SBAR->S). What is the meaning of
these unary rules?

What does it mean when the tag doesn’t change; for example, in sentence
“New England Electric, based in Westborough, Mass had offered $2 billion to
acquire PS of New Hampshire, well below the $2.29 billion value United
Illuminating places on its bid and the $2.25 billion Northeast says its bid
is worth.” whose phrase structure like:

(S (NP (NP (NNP New) (NNP England) (NNP Electric)) (, ,) (VP (VBN based)
(PP (IN in) (NP (NP (NNP Westborough)) (, ,) (NP (NNP Mass.))))) (, ,)) (VP
(VBD had) (VP (VBN offered) (NP (NP (QP ($ $) (CD 2) (CD billion)))) (S (VP
(TO to) (VP (VB acquire) (NP (NP (NNP PS)) (PP (IN of) (NP (NNP New) (NNP
Hampshire))))))) (, ,) (PP (ADVP (RB well)) (IN below) (NP (NP (NP (DT the)
(ADJP (QP ($ $) (CD 2.29) (CD billion))) (NN value)) (SBAR (S (NP (NNP
United) (NNP Illuminating)) (VP (NNS places) (PP (IN on) (NP (PRP$ its) (NN
bid))))))) (CC and) (NP (NP (DT the) (QP ($ $) (CD 2.25) (CD billion)))
(SBAR (S (NP (NNP Northeast)) (VP (VBZ says) (SBAR (S (NP (PRP$ its) (NN
bid)) (VP (VBZ is) (ADJP (IN worth))))))))))))) (. .))

the “(NP (NP …” has a unary relation between NP and NP (“(NP (NP (QP ($ $)
(CD 2) (CD billion))))”).

Thanks in advance.
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