From the reviews of the second edition: "This book provides an excellent introduction to ontologies. ... It has many examples illustrating to the reader the different characteristics of ontologies ... . One of the strengths of the book is that it is presented in the context of the semantic web ... . The book is a good blend of theory, applications and illustrations of ontologies. ... provides depth and insight into key problems of ontologies. ... provides the reader with a large number of references. ... Many of the references are new ... . To summarize, this is an excellent book ... ." (Daniel O'Leary, The Computer Journal, Vol. 48 (4), 2005)