I was asked recently about the motivation for Abney’s DP (determiner phrase) hypothesis. That is, that determiners are not part of English noun phrases but head up their own phrases of which NPs are complements. I couldn’t remember the justification I was given in my Syntax I class, so I went back to the textbook (Syntax: A Generative Introduction by Andrew Carnie). I found the following interesting excerpt:

“… for lack of a better place to put them, we put determiners … in the specifiers of NPs. This, however, violates one of the basic principles underlying X-bar theory: All non-head material must be phrasal. Notice that this principle is a theoretical rather than an empirical requirement (i.e., it is motivated by the elegance of the theory and not by any data), but it is a nice idea from a mathematical point of view, and it would be good if we could show that it has some empirical basis.”

This clashes a bit with my empirical sensibilities. It represents very much the rational point of view in linguistics, that we can probe our own understanding of language by judging what we perceive to be grammatical or ungrammatical. The empiricist view would look at it from another angle: does it appear in data? So the theoretical view might be “nice” but if it is not supported by the data, it is crap.

Treebanks don’t use DPs (at least none that I’ve seen), so automatic parsers typically have no concept of them. I wonder if they would add any value?  I’m guessing they would just run into sparsity issues since another set of tags have to be estimated.   But who knows, the extra structure might be helpful in complex situations.