This book fills the gap between vague waffle about 'Web 3' and the very detailed W3C specs.
It starts by examining the motivation for adding semantics to the web and then dives into the stack of technologies available for modeling information, reasoning about that information and making inferences based upon that reasonoing. Starting with RDF, it works coherently through RDFS, RDFS-Plus and OWL with concise and comprehnsible examples and challenges. These examples amount to a pattern catalogue (a view that is further reinforced by special purpose FAQ/Index) that is invaluable to new (and not-so-new) ontologists.
Along the way you also get introduced to the 3 concepts that make working with the Semantic Web so different from (for example) OO modeling: 1) Anyone can say Anything about Any topic (AAA) 2) Open World Assumption (OWA) - just because you haven't seen a piece of information yet , you can't assume that it doesn't exist 3) Unique Naming Assumption (UNA) - the same entity might be known by more than one name
A couple of "In The Wild" chapters describe aspects of actual implementations - from Friend Of A Friend (FAOF) to the National Cancer Institute Ontology (NCIO). These chapters are interesting because they demonstrate some of the concepts described in earlier chapters and root the discussion in practical applications.
A chapter on good & bad modeling practices is also indispensable, as it lists some of the common antipatterns that crop up when OO practitioners begin working with semantic modeling. The final chapter discusses the different dialects/species of OWL and begins to scratch the surface of the formal underpinnings of the technology. It also looks forward to what might be included in the next version of OWL, which is currently being designed.
The book has its fair share of typos, but is generally well laid out and easy to follow.
Some things that you won't find in this book:
- there's no "code"
- there's no discussion of toolsets that implement the technology
- you get introduced to N3 notation, but not RDF/XML
- there's no detail about query languages such as SPARQL
In short, this is book that gives you the understanding to work with the technology, not a book that describes low level details or specific implementations.