tailieunhanh - Báo cáo khoa học: "A FLEXIBLE NATURAL LANGUAGE PARSER BASED ON A TWO-LEVEL REPRESENTATION OF SYNTAX"

In this paper we present a parser which al lows to make explicit the interconnections between syntax and semantics, to analyze the sentences in a quasi-deterministic fashion and, in many cases, to identify the roles of the various constituents even if the sentance is ill-formed. The main fea ture of the approach on which the parser is based consists in a two-level representation of the sy_n tactic knowledge: a first set of rules emits h~ potheses about the constituents of the sentence and their functional role and another set of rules verifies whether a hypothesis satisfies the con straints. | A FLEXIBLE NATURAL LANGUAGE PARSER BASED ON A TWO-LEVEL REPRESENTATION OF SYNTAX Leonardo Lesmo and Pietro Torasso Istituto di Scienze dell Informazione Università di Torino Massimo D Azeglio 42 - 10125 TORINO - ITALY ABSTRACT In this paper we present a parser which al lows to make explicit the interconnections between syntax and semantics to analyze the sentences in a quasi-deterministic fashion and in many cases to identify the roles of the various constituents even if the sentance is ill-formed. The main fe ture of the approach on which the parser is based consists in a two-level representation of the syn tactic knowledge a first set of rules emits h potheses about the constituents of the sentence and their functional role and another set of rules verifies whether a hypothesis satisfies the con straints about the well-formedness of sentences. However the application of the second set of rules is delayed until the semantic knowledge con firms the acceptability of the hypothesis. If the semantics reject it a new hypothesis is obtained by applying a simple and relatively unexpensive natural modification a set of these modifica tions is predefined and only when none of them is applicable a real backup is performed in most cases this situation corresponds to a case where people would normally garden path. INTRODUCTION The problem of performing an accurate syntac tic analysis of Natural Language sentences is still challenging for . people working in the field of . interpretation Charniak 81 Kaplan 82 . The most relevant points which attracted at tention recently are - the need of a strong connection between synta tic processing and semantic interpretation in order to reduce the space of the alternative syn tactic analyses Konolige 80 sidner et al. 81 Milne 82 - the convenience of a quasi-deterministic syntac tic analysis in order to reduce the computation al overhead associated with a heavy use of back up Marcus 80 - the convenience of an approach which .