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Distribution of Complementizers
Like other non-arguments, complementizers anchor an auxiliary tree (shown in
Figure 8.1) and adjoin to elementary clausal trees. The auxiliary
tree for complementizers is the only alternative to having a complementizer
position `built into' every sentential tree. The latter choice would mean
having an empty complementizer substitute into every matrix sentence and a
complementizerless embedded sentence to fill the substitution node. Our choice
follows the XTAG principle that initial trees consist only of the arguments of
the anchor8.6 - the S tree
does not contain a slot for a complementizer, and the COMP tree has only
one argument, an S with particular features determined by the complementizer.
Complementizers select the type of clause to which they adjoin through
constraints on the <mode> feature of the S foot node in the tree
shown in Figure 8.1. These features also pass up to the root node,
so that they are `visible' to the tree where the embedded sentence
adjoins/substitutes.
- {Tree $\beta$COMPs, anchored by that
The grammar handles the following complementizers: that, whether, if, for, and no complementizer, and the
clause types: indicative, infinitival, gerundive, past participial,
subjunctive and small clause (nom/prep). The <comp> feature in a clausal tree reflects the value of the
complementizer if one has adjoined to the clause.
The <comp> and <wh> features receive their root
node values from the particular complementizer which anchors the tree.
The COMPs tree adjoins to an S node with the feature <comp>=nil; this feature indicates that the tree does not already
have a complementizer adjoined to it.8.7 We ensure that there are no stacked complementizers by
requiring the foot node of COMPs to have <comp>=nil.
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XTAG Project
http://www.cis.upenn.edu/~xtag