Fixed and Flexible Phrase Structure: Coordination in Tree Adjoining Grammars

In this paper, we show how a CCG-like account for coordination can be constructed in the framework of lexicalized tree-adjoining grammars (TAGs) (Joshi, 1987; Schabes et al., 1988; Schabes, 1990). 2. In particular, we show how a fixed constituency can be maintained at the level of the elementary trees of lexicalized TAGs and yet be able to achieve the kind of flexibility needed for dealing with the so-called non-constituents. This is the key significance of this contribution. In a CCG, being a constituent is the same as being a function. We show that this need not be the case and standard notions of constituency can be maintained. The key idea is that we use the lexicalized trees of TAG as structured categories with the associated functional types. Because of lack of space, we will illustrate our ideas by examples only.