Currently, knowledge engineering is strongly related to the construction of shared knowledge bases or conceptual frameworks, often designated as ontologies. Ontologies play an active role in the realization of Semantic Web by providing the basis for inter-operability of heterogeneous systems. However, use of ontology in processing information embedded in text documents is still restricted as it is very difficult to predefine an unambiguous and exhaustive ontology for any domain. The context- dependent nature of natural language makes reasoning with text information even more complicated. This book, therefore, provides the theoretical foundations of ontological engineering and covers the practical aspects of ontology learning and enhancement into a fuzzy ontology structure to accommodate uncertainties of natural language. This book can serves as a valuable resource for practicing professionals and applied researchers who are working on building search engines, ontology engineering, text mining, and knowledge-based applications. This book also accommodates the needs of graduate-level students in knowledge engineering and management course.