Disambiguation by Information Structure in DRT

Disambiguation by Information Structure in DRT Kurt Eberle * Institut fiir Maschinelle Sprachverarbeitung Universitgt Stuttgart Azenbergstr. 12 D-70174 Stuttgart Abstract ~i%xt understanding and high quality machine translation often necessitate the disambiguation of ambigous struc- tures or lexical elements. Drawing in- ferences from the context can be a means for resolving semantic ambigu- ities. However, often, this is an ex-. pensive strategy that, in addition, not always comes up with a clear prefer- ence for one of the alternatives. In this paper, we argue that in a num- ber of cases deep semantic analyses can be avoided by taking into account the constraints that the alternative readings impose onto the information structure. To this end, we present a study of the arnbigous German adverb erst and point out the particular circumstances under which the given information structure disambiguates the adverb without fur- ther semantic analysis. 1 Introduction German erst is ambigous. Consider the following examples: (1) Peter zeigte erst auf die vierte Gliickszahl. a) Und dann auf die zweite. (Peter first pointed to the fourth lucky number. And then to the second.) b) Nicht zuvor auf die erste, zweite oder dlqtte. (Peter only pointed to the fourth lucky number. Not to the first, second or third.) c) Noeh nieht aufdie Nnfte. (Peter only pointed to the fourth lucky number so far. Not yet to the fifth.) The alternative contexts a) - e) determine the meaning of the first sentence of (1) according to *This paper describes research done within the Sonderforschunsbereich 3~0 at IMS. I would like to thank Anette Frank, Hans Kamp, Michael Schiehlen and the other members of the IMS semantics group for helpfull discussion. the disambiguating translations presented. 'rhe example testifies the following three uses of crsl: • In the context (1.a), the recipient under- stands the introduced event as the first of a sequence of events that he expects to be completed by the following text. We call this reading: the First of a Sequence-reading (FS). • In the context (1.b), the recipient under- stands erst as a signal of the speaker/writer that the occurrence of the reported event is not preceded by the occurrence of similar (al- ternative) events. We call this reading: the Exclusion of Preceding Alternatives- reading (EPA). • In the context (1.c), the recipient under- stands the event as element of a sequence of events, and the realization of the sequence, in particular the reported realization of the event at the textual perspective time, seems to be in retardation, with regard to some (previous) expectation about the realization dates of the sequence. We call this reading: the Retardation-reading (R). As can be seen from the example, the contextual disambiguation not only is needed for understand- ing the text, but is a prerequisite for high quality translation. In the literature, different lbrmalizations have been discussed ((KSn79), (LSb89), (Kgn91), (HR81) (the latter one for the similar noch and schon) and others). With respect to the focus ad- verb use (the cases (1.b) and (1.c); (1.a) …

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