GETARUN Parser: A Parser Equipped with Quantifier Raising and Anaphoric Binding Based on LFG

GETARUN, the system for text understanding developed at the University of Venice, is equipped with three main modules: a lower module for parsing where sentence strategies are implemented; a middle module for semantic interpretation and discourse model construction which is cast into Situation Semantics; and a higher module where reasoning and generation takes place. We assume that from a psycholinguistic point of view, parsing requires setting up a number of disambiguating strategies, basically to tell arguments apart from adjuncts and reduce the effects of backtracking. The system is based on LFG theoretical framework and has a highly interconnected modular structure. It is a top-down depth-first DCG-based parser written in Prolog which uses a strong deterministic policy by means of a lookahead mechanism with a WFST to help recovery when failure is unavoidable due to strong attachment ambiguity. It is divided up into a pipeline of sequential but independent modules which realize the subdivision of a parsing scheme as proposed in LFG theory where a c-structure is built before the f-structure can be projected by unification into a DAG. As to multilinguality, the basic tenet of the parser is based on a UG-like perspective, i.e. the fact that all languages share a common core grammar and may vary at the periphery: internal differences are taken care of by parameterized rules. The DCG grammar allows the specification of linguistic rules in a highly declarative mode: it works topdown and by making a heavy use of linguistic knowledge may achieve an almost complete deterministic policy. Parameterized rules are scattered throughout the grammar so that they can be activated as soon as a given rule is entered by the parser.