Mapping Scrambled Korean Senteces into English Using Synchronous TAGs

Synchronous Tree Adjoining Grammars can be used for Machine Translation. However, translating a free order language such as Korean to English is complicated. I present a mechanism to translate scrambled Korean sentences into English by combining the concepts of Multi-Component TAGs (MC-TAGs) and Synchronous TAGs (STAGs). 1 M o t i v a t i o n Tree Adjoining Grammars (TAGs) were first developed by Joshi, Levy, and Takahashi (Joshi et al., 1975). There are other variants of TAGs such as STAGs (Shieber and Schabes, 1990), and MC-TAGs (Weir, 1988). STAGs in particular can be used for machine translation and were applied to KoreanEnglish machine translation in a military message domain (Palmer et al., 1995). Park (Park, 1995) suggested a way of handling Korean scrambling using MC-TAGs together with a priority concept. However, as scrambled argument structures in Korean were represented as sets using MC-TAGs, a mechanism to combine MC-TAGs and STAGs was necessary to translate Korean scrambled sentences into English. 2 Korean-English Machine Translation Using STAGs STAGs are a variant of TAGs introduced to characterize correspondences between tree adjoining languages. They can be used to relate TAGs for two different languages for machine translation (Abeill6 et al., 1990). The translation process consists of three steps. The source sentence is parsed according to the source grammar. Each elementary tree in the derivation is considered with the features given from the derivation through unification. Second, the source derivation tree is transferred to a target derivation. This step maps each elementary tree in the source derivation tree to a tree in the target derivation tree by looking in the transfer lexicon. And finally, the target sentence is generated from the target derivation tree obtained in the previous step. The transfer lexicon consists of pairs of trees, one from the source language and the other from the target language. Within the pair of trees, nodes may be linked. Whenever adjunction or substitution is performed on a linked node in a source tree, the corresponding operation applies to the linked node in the target tree.