An English to Turkish Machine Translation System Using Structural Mapping

This paper describes the design and implementat ion of an English-Turkish machine translation (MT) system developed as a part of the TU-Language project supported by a NATO Science for Stability Project grant. The system uses a structural transfer approach in translating the domain of IBM computer manuals. The general design of the translation system and a detailed description of the transfer component is presented in this paper. 1 I n t r o d u c t i o n The TU-Language project sponsored by the NATO Science for Stability Programme was started in 1994 to establish computational foundations for the natural language processing research on the Turkish language with the collaboration of the Computer Engineering Department of Middle East Technical University, the Computer Science Department of Bilkent University and ttalici Computing, Inc. The project a t tempts to perform extensive research on Turkish which will eventually lead to the development of an English to Turkish machine translation system, Turkish language tutorial system, a Turkish dictionary and other software tools to be used in further research. In this paper, some issues in translating from English to Turkish languages, the translation domain, the outline of the machine translation system under development, and a detailed description of the transfer component will be presented. 2 T u r k i s h L a n g u a g e Morphology and syntax of Turkish are very different from English, therefore, the formalism used to represent English texts has to be altered significantly for Turkish text representation. The Turkish language is characterized as a head final language where the modifier/specifier always precedes the modified/specified. This characteristic also affects the word order of the sentences which can be described as SOV where the verb is positioned at the end. Also, when compared to other languages, Turkish relies more on overt case markings which mark the role of the argument in a sentence. The case markings enables Turkish to have a relatively free wordorder property where every variation in the word order in a sentence results in a different meaning. In the MT system being developed, these and other different characteristics of the Turkish language are handled in the transfer and generation components. 3 T r a n s l a t i o n D o m a i n As more and more computer companies enter the Turkish market, a growing demand for English to Turkish translation of computer manuals has emerged. Other machine translation systems have also chosen the domain of computer manuals for their translation systems because of the relatively unambiguous and narrow sublanguage used (Tsutsumi, 1986). Also, in his research, Nasukawa (Nasukawa, 1993) concluded that the statistical analysis of the text in IBM computer manuals showed that 92.6 percent of the words in a computer manual are used in the same word sense which would significantly reduce the problem of lexical ambiguity resolution. Another advantage is that the material in a computer manual is observed to be written as clearly as possible in a relatively narrow area which will hopefully ease the difficult job of understanding and representing the input sentence. As a result of these observations, the TULanguage project team has chosen the IBM computer manuals as their translation domain.. 4 M a c h i n e T r a n s l a t i o n S y s t e m The English to Turkish MT system under development uses a structural transfer approach which has the following components. First, the English sentence retrieved from the IBM manual is analyzed