A Conversation with Tim Bray: "JG Just what is RDF?
TB RDF is a general-purpose facility for expressing meta-data, which is to say assertions about resources. I use resource in the technical term, Web resource. So RDF models the world as a series of triples, where you have a resource, and then you have a resource-property-value triple, you have a resource that has a URI (uniform resource identifier), you have a property that also has a URI, and then a value that can be a literal value or another URI.
JG I generally identify RDF with the Semantic Web.
TB The whole Semantic Web was launched by the RDF activity and now has grown to include OWL (Web Ontology Language), which is a general knowledge representation language. But, boy, there are problems. The XML serialization of RDF is horrible; it's a botched job.
You know, KR didn't suddenly become easy just because it's got pointy brackets. Doug Lenat has been off working in the desert on that for decades and nobody has ever made a buck on it yet, as far as I know.
Motivating people to provide meta-data is tough. If there's one thing we've learned, it's that there is no such thing as cheap meta-data. The whole point was to make search run better at some level. Google showed us the power of what was always used in the academic citation index -- namely, the number of incoming links.
JG Inferring meta-data...
TB Inferring meta-data doesn't work. Google doesn't infer meta-data. It's a deterministic calculation based on finding links and counting links and doing transitive closures on that. Inferring meta-data by natural language processing has always been expensive and flaky with a poor return on investment.
I spent two years sitting on the Web consortium's technical architecture group, on the phone every week and face-to-face several times a year with Tim Berners-Lee. To this day, I remain fairly unconvinced of the core Semantic Web proposition. I own the domain name RDF.net. I’ve offered the world the RDF.net challenge, which is that for anybody who can build an actual RDF-based application that I want to use more than once or twice a week, I’ll give them RDF.net. I announced that in May 2003, and nothing has come close."
Jim Gray interviews Tim Bray. Read the entire interview if you care about the past, present, and future of XML. (Note: it's a 4-part interview and there doesn't seem to be a single-page view.)