The Semantic Web is a new area of research and development in the field of computer science, which aims to make it easier for computers to process the huge amount of information on the Web, and indeed other large databases, by enabling computers not only to read, but also understand the information. This book is intended to be a textbook about the Semantic Web and related topics, and is based on successful courses taught by the authors. They describe not only the theoretical issues underlying the semantic web, but also practical matters (such as algorithms, optimisation ideas and implementation details) and this aspect will make the book valuable as well to practitioners. Supplementary materials available via the web include include source the code of program examples, and the syntactic description of various languages.