Computing Lexical Cohesion as a Tool for Text Analysis

Recognizing coherent structure of a text is an essential task in natural language understanding. It is necessary, for example, to resolve anaphora, ellipsis, and ambiguity. One of the dominant factors of coherence of the text structure is lexical cohesion, namely the dependency relationship between words based on associative relations in common knowledge. This thesis proposes an objective and computationally feasible method for measuring lexical cohesion, especially semantic relations, between words. Lexical cohesion between words is computed on a semantic network constructed systematically from a subset of an ordinary English dictionary. Spreading activation on the semantic network analyses the meaning of a word into a 2,851-dimensional semantic space and computes the strength of lexical cohesion between any two words in the dictionary. As an evaluation of the measurement of lexical cohesion, this thesis then presents a quantitative indicator, Lexical Cohesion Profile (LCP), for segme..