Motivation for this Book Ontologies have received increasing attention over the last two decades. Their roots can be traced back to the ancient philosophers, who were interested in a c- ceptualization of the world. In the more recent past, ontologies and ontological engineering have evolved in computer science, building on various roots such as logics, knowledge representation, information modeling and management, and (knowledge-based) information systems. Most recently, largely driven by the next generation internet, the so-called Semantic Web, ontological software engineering has developed into a scientific field of its own, which puts particular emphasis on the theoretical foundations of representation and reasoning, and on the methods and tools required for building ontology-based software applications in diverse domains. Though this field is largely dominated by computer science, close re- tionships have been established with its diverse areas of application, where - searchers are interested in exploiting the results of ontological software engine- ing, particularly to build large knowledge-intensive applications at high productivity and low maintenance effort. Consequently, a large number of scientific papers and monographs have been p- lished in the very recent past dealing with the theory and practice of ontological software engineering. So far, the majority of those books are dedicated to the thoretical foundations of ontologies, including philosophical treatises and their re- tionships to established methods in information systems and ontological software engineering.