Controlling the Application of Lexical Rules
Ted Briscoe, Ann Copestake · 1996
In this paper, we describe an item-familiarity account of the semi-productivity of morphological and lexical rules, and illustrate how it can be applied to practical issues which arise when building large scale lexical knowledge bases which utilize lexical rules. Our approach assumes that attested uses of derived words and senses are explicitly recorded, but that productive use of lexical rules is also possible, though controlled by probabilities associated with rule application. We discuss how the necessary probabilities and estimates of lexical rule productivity may be acquired from corpora. 1 IntrodUction Lexicalist linguistic theories, such as HPSG, LFG and categorial grammar, rely heavily on lexical rules. Recently, techniques have been described which address the efficiency issues that this raises for fully productive rules, such as inflectional rules and 'syntactic rules' (such as the HPSG complement extraction lexical rule). For example, Bouma &: van Noord (1994) and Johnson &: Dorre (1995) propose techniques for delayed evaluation of lexical rules so that they apply 'on demand' at parse time. Meurers &: Minnen (1995) present a covariation approach, in which a finite-state machine for the application of lexical rules is derived by computing possible follow relations between the set of rules and then pruned FSMs are associated with classes of actual lexical entries representing the restricted set of rules which can apply to those entries. Finally, entries themselves are extended with information common to all their derived variants. These techniques achieve most of the advantages of lexicon expansion in the face of recursive rules and cyclic rule interactions which preclude a full off-line expansion.