Expert Systems and Other New Techniques in MT Systems

EXPERT SYSTEMS AND OTHER NEW TECHNIQUES IN MT SYSTEMS Christian BOITET - Ren~ GERBER Groupe d'Etudes pour la Traduction Automatique BP n ° 68 Universit~ de Grenoble 38402 Saint-Martin d'H~res FRANCE ABSTRACT Our MT systems integrate many advanced con- cepts from the fields of computer science, linguis- tics, and AI : specialized languages for linguistic programming based on production systems, complete linguistic programming environment, multilevel representations, organization of the lexicons around "lexical units", units of translation of the size of several paragraphs, possibility of using text-driven heuristic strategies. We are now beginning to integrate new techni- ques : unified design of an "integrated" lexical data-base containing the lexicon in "natural" and "coded" form, use of the "static grammars" forma- lism as a specification language, addition of expert systems equipped with "extralinguistic" or "metalinguistic" knowledge, and design of a kind of structural metaeditor (driven by a static grammar) allowing the interactive construction of a document in the same way as syntactic editors are used for developing programs. We end the paper by mentioning some projects for long-term research. INTRODUCTION In this paper, we assume some basic knowledge of CAT (Computer Aided Translation) terminology (MT, M.AHT, HAMT, etc.). The starting point of our research towards "better" CAT systems is briefly reviewed in I. In II, we present 3 lines of current work : improving current second-generation metho- dology by incorporating advanced techniques from software engineering, moving toward third-genera- tion systems by incorporating expert systems, and returning to interactive techniques for the creation of a document. 1 - IMPORTANT CONCEPTS FROM EXISTING SYSTEMS For lack of space, we only list our major points, and refer the reader to (3,4,5,6,15) for further details. ! - Computer science aspects i) Use of Specialized Languages for Linguistic Programming (SLLP), like ATEF, ROBRA, Q-systems, REZO, etc. 2) Integration in some "user-friendly" envi- ronment, controlled by a conversational interface, and managing a specialized data-base composed of what we call "lln~-~are" (grammars, dictionaries, procedures, formats, variables~ and corpuses of texts (source, translated, revised, plus intermediate results and possibly "hors-textes" -- figures, etc.). 3) Analogy with compiler-compiler systems : rough translation is realized by a monolingual analysis, followed by a bilingual transfer, and then by a monolingual generation (synthesis). 2 - Linguistic aspects I) Only linguistic levels (of morphology, syntax, logico-semantics, modality, actualisation, ...) are used, leading to some implicit understan- ding, characteristic of second-generation MT systems. 2) Hence, the extralinguistic levels (of expertise and pragmatics) which furnish some degree of explicit understanding are beyond the limits of second-generation CAT systems. 3) During analysis of a unit of translation, computation of these (linguistic) levels is not done sequentially, but in a cooperative way. Analysis produces the analog of an "abstract tre@'~ namely a multilevel interface structure to repre- sent all the computed levels on the same graph (a "decorated tree"). 4) Lexical knowledge is organized around the notion of lexical unit (LU), allowing for powerful paraphrasing capability. 5) The texts are segmented into translation units of one or more paragraphs. …

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