The Lexicon-Grammar Balance in Robust Parsing of Italian

What is the role of lexical information in robust parsing of unrestricted texts? In this paper we provide experimental evidence showing that, in order to strike the balance between robustness and coverage needed for practical NLP applications, judicious use of positive lexical evidence given a text should be complemented with a battery of dynamic parsing strategies aimed at solving local constraint conflicts. Likewise, negative lexical evidence should not blindly override grammatical information. Unlike fully lexicalised approaches to parsing where cross-categorial constraints on lexicon usage apply freely, optimal results can be obtained by modulating the way subcategorisation information is brought to bear in identifying dependency relations in context.