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 anchor<sup>8.6</sup> - the S tree does not contain a slot for a complementizer, and the $\beta$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.

  

Figure: 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 $\beta$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 $\beta$COMPs to have <comp>=nil.