With the explosion of available textual data on the Web, the importance of mapping textual contents into structured representation through automatically harvesting semantic relations from unstructured text has been recognized. In this book, we systematically study two types of relation extraction: relation extraction for linguistic parsing and that for semantic repository construction. For the first type, we investigate the identification of elements from each sentence and their arrangements in a structured format. For the second type, we focus on the extraction of relations between named...