Complex Verb Transfer Phenomena in the SLT System

COMPLEX VERB TRANSFER PHENOMENA IN THE SLT SYSTEM Björn Gambäck Ivan Bretan1 gamback@sics.se ivan@sics.se Natural Language Processing Group Swedish Institute of Computer Science Box 1263, S - 164 28 Kista, Stockholm, Sweden Abstract The paper discusses several complex transfer problems and their prospective solutions within an English-to-Swedish spoken language translation system. The emphasis in the text is on transfer problems which are not lexically triggered, concentrating mainly on the translation of differences in mood and tense. Laying the groundworks for the trans- lation part, the treatment of verb-phrase syntax and semantics is described in detail. The paper also shortly discusses some lexically triggered complex transfer problems. 1 Introduction When developing a system aimed at translating between two natural languages, several problems soon emerge. Some of these are specific to the translation methodology chosen or the language-pair at hand, while others can be generalized and tend to occur in any translation system. Many of the problems of the general kind are rooted in the verb-phrases; phrases that not only show a rich cross-linguistic variety, but also are of vital importance for the interpretation of utterances in almost any language. In this paper we will discuss some of these problematic transfer phenomena, mainly concentrating on those that arise as an effect of tense and mood differences. The problems concerning complex transfer may in general be split into two quite different categories, those that are and those that are not lexically triggered. The first group contains such phenomena as argument- and head switching, object raising, and changes from one syntactic category to another. The second group includes problems with changes in aspect, tense, mood, and determination. The question of lexically triggered complex transfer problems is not the main topic of this paper — a nice overview of such problems as having surfaced in several other systems can be found in (Pulman (ed.) 1991) — although some such problems will be discussed in Section 4. The framework for our discussion there, as well as in the entire paper as such, is the transfer component of a spoken-language English-to-Swedish translation system called SLT, a short overview of which is the topic of Section 2. The transfer formalism used in the SLT system is the general point of discussion in Section 3. The main problem addressed in the paper is that of translating verb-phrases. The syntactic and semantic treatment of these in our grammars is thus the topic of Section 5. The discussion in that section is mainly centered around the treatment of tense and mood; our solution to translating these phenomena is then described in Section 6. Finally, Section 7 sums up the previous discussion and points to some areas of future research. 'Thanks to Jussi Karlgren, Manny Rayner, Christer Samuelsson and Mats Wirén for valuable comments. 89 2 The SLT system The Spoken Language Translator (SLT) is a system prototype which can translate queries from spoken English to spoken Swedish in the domain of air travel planning (ATIS). The system was developed as a …

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