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Topicalization and the value of the <inv> feature
Our analysis of topicalization uses the same trees as wh-extraction. For any
NP complement position a single tree is used for both wh-questions and for
topicalization from that position. Wh-questions have subject-auxiliary
inversion and topicalizations do not. This difference between the
constructions is captured by equating the values of the Sr's <inv> feature and the extracted NP's <wh> feature. This means
that if the extracted item is a wh-expression, as in wh-questions, the value of <inv> will be + and an inverted auxiliary will be forced to
adjoin. If the extracted item is a non-wh, <inv> will be -
and no auxiliary adjunction will occur. An additional complication is that
inversion only occurs in matrix clauses, so the values of <inv> and <wh> should only be equated in matrix clauses and not in embedded
clauses. In the English XTAG grammar, appropriate equating of the <inv> and <wh> features is accomplished using the <invlink> feature and a restriction imposed on the root S of a
derivation. In particular, in extraction trees that are used for both
wh-questions and topicalizations, the value of the <inv> feature for
the top of the Sr node is co-indexed to the value of the <inv>
feature on the bottom of the Sq node. On the bottom of the Sq node
the <inv> feature is co-indexed to the <invlink> feature.
The <wh> feature of the extracted NP node is co-indexed to the value
of the <wh> feature on the bottom of Sq. The linking between the
value of the Sq <wh> and the <invlink> features is
imposed by a condition on the final root node of a derivation (i.e. the top S
node of a matrix clause) requires that <invlink>=<wh>. For
example, the tree in Figure 14.1 is used to
derive both ((190)) and ((191)).
(189)0(189
- (190)
- John, I like.
(190)0(190
- (191)
- Who do you like?
For the question in ((191)), the extracted item who has the feature
value <wh>=+, so the value of the <inv> feature on VP is
also + and an auxiliary, in this case do, is forced to adjoin. For the
topicalization ((190)) the values for John's <wh> feature and
for Sq's <inv> feature are both - and no auxiliary
adjoins.
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XTAG Project
http://www.cis.upenn.edu/~xtag