In the mid-1990s, I happened upon the topic of conceptual graphs (CGs), which are a way to represent formal logic statements using diagrams. I was accustomed to entity-relationship (ER) modeling, and I was immediately fascinated by CGs because they seemed so expressive and natural, a tremendously useful extension of ER diagrams. Also, they had grown out of efforts to represent expression in natural language, and because of this it was easy to read off the contents of a graph in English. In 1999 I discovered topic maps, which instantly struck me as a simplified implementation of CGs, one that was well suited to hooking into the Web.
I had no project at work that justified my spending much time on these subjects, but I began to study them when I could and to introduce them to others. A year or two later, I started to come across mentions of RDF and then of the Semantic Web; I began to fit them into my mental picture, which by now included distributed databases and web applications, markup languages such as HTML and XML, and of course CGs and topic maps.
I found the Semantic Web the hardest of all to get a handle on, because it seemed to range from obvious extensions of what I already knew on the one extreme, to extremely complex and advanced integrations of logic, semantics, and artificial intelligence on the other. I now know that I was not the only one to become bewildered, yet fascinated, by the Semantic Web.
One other such person was Marjan Bace, publisher of Manning. The Semantic Web came up by chance during a phone conversation we had, and before I quite knew how it had come about, Manning had a new book project and I was off and running. At the time, I had no idea how demanding the work would be (although I thought I did) nor how long it would take (although I thought I did). The Semantic Web hooks into an enormous number of technologies and disciplines, and they all have to work together in complex and nonlinear ways. It is too much for a single person to know intimately, yet the author's job is to make it clear and understandable to the reader. That's what this book attempts to do: make this fascinating and complex subject clear, concise, and accessible.