Types in Functional Unification Grammars

In this paper, we present several extensions to the FU formalism that address these limitations. These extensions are based on the formal semantics Functional Unification Grammars (FUGs) are presented in (Elhadad, 1990). They have been impopular for natural language applications because the plemented and tested on several applications. formalism uses very few primitives and is uniform and expressive. In our work on text generation, we have found that it also has annoying limitations: it is not We first introduce the notion of typed features. It suited for the expression of simple, yet very common, allows the definition of a structure over the primitive taxonomic relations and it does not allow the symbols used in the grammar. The unifier can take specification of completeness conditions. We have advantage of this structure in a manner similar to (Aitimplemented an extension of traditional functional Kaci, 1984). We then introduce the notion of typed unification. This extension addresses these limitations constituents and the FSET construct. It allows the decwhile preserving the desirable properties of FUGs. It laration of explicit constraints on the set of admissible is based on the notions of typed features and typed paths in functional descriptions. Typing the primitive constituents. We show the advantages of this extenelements of the formalism and the constituents allows sion in the context of a grammar used for text generaa more concise expression of grammars and better tion. checking of the input descriptions. It also provides more readable and better documented grammars. Most work in computational linguistics using a