This book is all about the Semantic Web. From its basics, the Semantic Web can be viewed as a collection of standards and technologies that allow machines to understand the meaning (semantics) of informa- tion on the Web. It represents a new vision about how the Web should be constructed so that its information can be processed automatically by machines on a large scale. This exciting vision opens the possibility of numerous new applications on the Web. Since 2001, there have been many encouraging results in both academic world and real application world. A whole suite of standards, technologies, and related tools have been specified and developed around the concept of the Semantic Web.