tailieunhanh - Báo cáo khoa học: "Efficient Construction of Underspecified Semantics under Massive Ambiguity"

We investigate the problem of determining a compact underspecified semantical representation for sentences that may be highly ambiguous. Due to combinatorial explosion, the naive method of building semantics for the different syntactic readings independently is prohibitive. We present a method that takes as input a syntactic parse forest with associated constraintbased semantic construction rules and directly builds a packed semantic structure. The algorithm is fully implemented and runs in O(n4log(n)) in sentence length, if the grammar meets some reasonable 'normality' restrictions. . | Efficient Construction of Underspecified Semantics under Massive Ambiguity Jochen Dôrre Institut fur maschinelle Sprachverarbeitung University of Stuttgart Abstract We investigate the problem of determining a compact underspecified semantical representation for sentences that may be highly ambiguous. Due to combinatorial explosion the naive method of building semantics for the different syntactic readings independently is prohibitive. We present a method that takes as input a syntactic parse forest with associated constraintbased semantic construction rules and directly builds a packed semantic structure. The algorithm is fully implemented and runs in ơ n4 op n in sentence length if the grammar meets some reasonable normality restrictions. 1 Background One of the most central problems that any NL system must face is the ubiquitous phenomenon of ambiguity. In the last few years a whole new branch developed in semantics that investigates underspecified semantic representations in order to cope with this phenomenon. Such representations do not stand for the real or intended meaning of sentences but rather for the possible options of interpretation. Quantifier scope ambiguities are a semantic variety of ambiguity that is handled especially well by this approach. Pioneering work in that direction has been Alshawi 92 and Reyle 93 . More recently there has been growing interest in developing the underspecification approach to also cover syntactic ambiguities cf. Pinkal 95 EggLe-beth 95 Schiehlen 96 . Schiehlen s approach is outstanding in that he fully takes into account syntactic This research has been carried out while the author visited the Programming Systems Lab of Prof. Gert Smolka at the University of Saarland Saarbriicken. Thanks to John Maxwell Martin Miiller Joachim Niehren Michael Schiehlen and an anonymous reviewer for valuable feedback and to all at PS Lab for their helpful support with the oz system. constraints. In Schiehlen 96 he presents an algorithm .