Sublanguages in Machine Translation

SUBLANGUAGES IN MACHINE TRANSLATION Heinz-Dirk Luckhardt Fachrichtung 5.5 lnformationswissenschaft Universit~it des Saarlandes D-6600 Saarbriicken, Federal Republic of Germany ABSTRACT There have been various attempts at using the sublanguage notion for disambi- guation and the selection of target language equivalents in machine translation. In this paper a theoretical concept and its imple- mentation in a real MT application are pre- sented. Above this, means of linguistic engineering like weighting mechanisms are proposed. INTRODUCTION It has been proposed by a number of authors (cf. Kittredge 1987, Kittredge/Lehr- berger 1982, Luckhardt 1984) to use the sublanguage notion for solving some of the notorious problems in machine translation (MT) such as disambiguation and selection of target language equivalents. In the following, I shall give a rough summary of what sublanguages can contri- bute to the solution of concrete MT pro- blems. A SUBLANGUAGE CONCEPT FOR USE IN MT SYSTEMS To my knowledge, it was Z. Harris who introduced the term 'sublanguage' (cf. Harris 1968, 152) for a portion of natural language differing from other portions of the same language syntactically and/or lexically. Definitions are gwen by Hirschman/Sager (1982), Quinlan (1989) and Lehrberger (1982). In order to be able to use such characterizations in MT, they have to be formalized in a way adequate to the MT system in question. Such formalizable properties were combined in the definition of Luckhardt (1984) of what sublanguage can mean for MT: Text type represents the syntactic-syntagmatic level of a sublangua- ge for which only a rather weak differentiation can be proposed (e.g. running text, word list, nominal structures etc.). Subiect field represents the lexical level of a sublanguage, i.e. for every sublanguage a subject field is determined as being characteristic, so that the MT system may choose on the basis of the sublanguage of a text those translation equivalents from the lexicon which carry the same subject field code as the translated text. The lack of a commonly accepted subject field classification for MT Is a serious problem. Such a classification is tentatively proposed in Luckhardt/Zimmer- mann 1991. T~xt function represents the lexical- pragmatic level. The function of a text (or its target group) may determine the choice of TL equivalents and of syntactic structure or style. The inhouse usage criterion covers a number of aspects determined by special requests of the MT user or the firm ordering the translation. This is first of all a question of inhouse terminology. SUBLANGUAGES FOR MT: MAINTENANCE REQUIREMENTS A typical maintenance requirement card of the Bundessprachenamt (Federal Translati- ons Agency) among others contains the fol- lowing parts: . 0esignation of eauipment text type 'nominal structure' text function 'title' e.g.: 'Portable gasoline driven pump' . tools, parts, material~ text type 'word list' text function 'accessories'; e.g.: - key set, head screw, L-type hex - wrench, adjustable, open end 6" - solvent, type II - screwdriver, flat tip, medium duty - rags, wiping - 306 - 3. the basis of word order: orocedure text type 'instructions' (imperative style) text function 'maintenance instructions', e.g.: …

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