Why is RDF worth our time? My short answer is "because RDF is loose, but not too loose." RDF has enough order to do useful things, but doesn't require us to rewire the world first. If tech were tunes, RDF would be a jazz trio, not a Bach fugue. It lets players who hardly know each other improvise, yet it holds things together beautifully: the quintessential jam.

In this way, RDF is much like the current Web. RDF shares many of the benefits that made the first Web a success. As Dave Beckett said, "RDF allows loose collaboration with little pre-coordination, links can break, anyone can link." The world and the web are just too much of a mess to make neat, which is why the first Web flourished, because people could stitch it together a bit at a time without first clearing things with their head librarian. But the first Web has problems: it's too loose. If RDF is a jazz trio, the first Web is more like street noise ... a crazy cacophony of unrelated content.

So how does RDF achieve this balance of form and freedom? First, it pins things down with URIs. In RDF, resources and predicates and ontologies all use well-defined, world-referencable, names. This grounds the model, giving us a shared vocabulary to work with. Even better, we're not restricted by the structure; our vocabularies can continually evolve without breaking the system.

Second, RDF statements are piecemeal in nature. You and I can describe the same resource in complementary ways and never know each other. Along comes a search bot and combines our statements, giving us a larger understanding of the resource than either of us had. This "semantic interleaving" gives RDF much of its freedom. Combine this with RDF's flexible vocabularies, and we've got a description scheme that's just "webby" enough to work. It's loose, but not too loose.

I'll talk more about these benefits in future "yarns." There's only so much I can say without real-world examples, so I'll underline these points further as I explore the products and ontologies that are built with RDF.