Thai Text Coherence Structuring with Coordinating and Subordinating Relations for Text Summarization

Text summarization with the consideration of coherence can be achieved by using discourse processing with the Rhetorical Structure Theory (RST). Additional problems on relational ambiguity may arise, especially in Thai. For example, the use of cue words, i.e. "tae/???" (meaning "but"), can be identified as a contrast relation or an elaboration relation. Therefore, we propose the reduction of the ambiguity level by reducing the relation types to two, namely Coordinating and Subordinating relation. Our framework is to concentrate on coherence structuring which requires the following 3 steps: (1) identify an attachment point for an incoming discourse unit by using our Adaptive Right-frontier algorithm; (2) extract Coordinating and Subordinating relations through the identification of linguistic coherence features in the lexical and phrasal level, using Bayesian techniques; (3) construct coherence tree structures, The accuracy is 70.45% for the first step, 77.47% and 79.89% for COR and SUBR extraction respectively in the second step and 64.94% in constructing coherent tree of the third.