This book examines key issues in designing semantics-oriented natural language processing systems. A broad conceptual framework for describing structured meanings of NL-texts is obtained by defining a new class of formal languages called standard knowledge languages (SK-languages) using a system theoretical approach. Readers will gain knowledge of these languages and will learn a way of building semantic representations using them. With extensive use of examples and illustrations to clarify complex material and demonstrate practical applications, generous historical and bibliographical notes, end-of-chapter exercises, and glossaries, this book will serve as an ideal graduate-level textbook, as well as a good reference for researchers and practitioners who deal with the various problems involving semantics of natural language texts.