Slot Unification Grammar
Antonio Ferrández, Manuel Palomar, Alicante University, L. Moreno · 1997
In this paper we propose a framework which we call Slot Unification Grammar (SUG). This framework allows to integrate different kinds of knowledge, all of them necessary for resolution of several problems in Natural Language Processing (NLP). These problems, such as coordination, extraposition of constituents, ellipsis and anaphora, sometimes occur simultaneously and it is very useful to solve them in a modular way. This framework includes a grammatical formalism which makes easier the solution of these problems. This formalism is based on unification and it is an extension of Definite Clause Grammar (DCG). SUG extends DCG in the following characteristics: (1) SUG allows optional subconstituents in any production rule without adding new nonterminal symbols; (2) SUG solves coordination and juxtaposition by means of its predicates coordination and juxtaposition. We have implemented SUG in Prolog, extending DCG in the following way: (3) SUG automatically returns a slot structure which integrates syntactic, morphologic and semantic information of every constituent of the grammar; (4) SUG will access to the dictionary only once during the whole process of parsing; (5) SUG will generate the logical formula of a sentence after solving the above problems, allowing us to generate very modular NLP systems. 1.