Translating Idioms

This paper discusses the t reatment of fixed word expressions developed for our ITS-2 FrenchEnglish translation system. This t reatment makes a clear distinction between compounds i.e. mult iword expressions of X°-level in which the chunks are adjacent and idiomatic phrases i.e. mult iword expressions of phrasal categories, where the chunks are not necessarily adjacent. In our system, compounds are handled during the lexical analysis, while idioms are treated in the syntax, where they are t reated as "specialized lexemes". Once recognized, an idiom can be transfered according to the specifications of the bilingual dictionary. We will show several cases of transfer to corresponding idioms in the target language, or to simple lexemes. The complete system, including several hundreds of compounds and idioms can be consulted on the Internet (ht tp : / / lat l .unige.ch/i tsweb.html). 1 I n t r o d u c t i o n Multiword expressions (henceforth MWE), are known to constitute a serious problem for natural language processing (NLP) 1. In the case of translation, a proper t reatment of MWE is a fundamental requirement, as few customers would tolerate a literal translation of such common expressions as entrer en vigueur 'to come into effect', met t re en oeuvre 'to implement ' , faire preuve 'to show' or faire connaissance 'to meet '. " I am grateful to Anne Vandeventer, Christopher Laenzlinger and Thierry Etchegoyhen for helpful comments. Part of the work described in this paper has been supported by a grant from CTI (grant no 2673.1). zCf. Abeill~ & Schabes (1989), Arnold et al. (1995), Laporte (1988), Schenk (1995), Stock (1989), among others. However, a simple glance at some of the current commercial translation systems shows that none of them can be said to handle MWEs in an appropriate fashion. As a mat te r of fact, some of them explicitely warn their users not to use multiword expressions. In this paper, we will first stress some fundamental properties of two classes of MWEs, c o m p o u n d s and i d i o m s , and then present the t reatment of idioms developed for our FrenchEnglish ITS-2 translation system (cf. Ramluckun & Wehrli, 1993). 2 Compounds and idioms A two-way part i t ion of MWEs in (i) compounds and (ii) idioms is both convenient and theoretically well-motivated 2. Compounds are defined as MWEs of X°-level (ie. word level), in which the chunks are adjacent, as exemplified in (1), while "idiomatic expressions" correspond to MWEs of phrasal level, where chunks may not be adjacent, and may undergo various syntactic operations, as exemplified in (2-3). (1)a. pomme de terre 'potato ' b. ~ cause de 'because of' c. d~s lors que 'as soon as' The compounds given in (1) function, respectively, as noun, preposition and conjunction. They correspond to a single unit , both syntactically and semantically. In contrast, idiomatic expressions do not generally constitute fixed, closed syntactic units. They do, however, behave as semantic units. For instance the complex syntactic expression casser du sucre sur le dos de quelqu'un, literally break some sugar on ~This distinction between compounds and idioms is also discussed in Wehrli (1997)