MACHINE TRANSLATION: HISTORY AND GENERAL PRINCIPLES

The translation of natural languages by machine, first dreamt of in the seventeenth century, has become a reality in the late twentieth. Computer programs are producing translations - not perfect translations, for that is an ideal to which no human translator can aspire; nor translations of literary texts, for the subtleties and nuances of poetry are beyond computational analysis; but translations of technical manuals, scientific documents, commercial prospectuses, administrative memoranda, medical reports. Machine translation is not primarily an area of abstract intellectual inquiry but the application of computer and language sciences to the development of systems answering practical needs. After an outline of basic features and general methods, the history of machine translation is traced from the pioneers and early systems of the 1950s and 1960s, the impact of the ALPAC report in the mid-1960s, the revival in the 1970s, commercial and operational systems of the 1980s, and research during the 1980s. 1. Basic features and terminology The term machine translation (MT) refers to computerized systems responsible for the production of translations with or without human assistance. It excludes computer-based translation tools which support translators by providing access to on-line dictionaries, remote terminology databanks, transmission and reception of texts, etc. The boundaries between machine-aided human translation (MAHT) and human-aided machine translation (HAMT) are often uncertain and the term computer-aided translation (CAT) can cover both, but the central core of MT itself is the automation of the full translation process. Although the ideal goal of MT systems may be to produce high-quality translation, in practice the output is revised ('post-edited'). It should be noted that in this respect MT does not differ from the output of most human translators which is normally revised by a second translator before dissemination. However, the types of errors produced by MT systems do differ from those of human translators (incorrect prepositions, articles, pronouns, verb tenses, etc.). Postediting is the norm, but in certain circumstances MT output may be unedited or only lightly revised, e.g. if it is intended only for specialists familiar with the text subject. Output might also serve as a rough draft for a human translator, i.e. as a 'pre-translation'. The translation quality of MT systems may be improved either, most obviously, by developing more sophisticated methods or by imposing certain restrictions on the input. The system may be designed, for example, to deal with texts limited to the 'sublanguage' (vocabulary and grammar) of a particular subject field (e.g. biochemistry) and/or document type (e.g. patents). Alternatively, input texts may be written in a 'controlled language', which restricts the range of vocabulary, avoids homonymy and polysemy and complex sentence structures. A third option is to require input texts to be marked ('pre-edited') with indicators of prefixes, suffixes, word divisions, phrase and clause boundaries, or of different grammatical categories (e.g. the noun co'nvict and its homonymous verb convi'ct). Finally, the system itself may refer problems of ambiguity and selection to human operators (usually translators) for resolution during the