Jim Hendler continues his exploration of the dark side of the semantic web with a must-read editorial for IEEE Intelligent Systems, the well-respected AI journal:
A key realization that Berners-Lee had with respect to the design of RDF is having unique names for different terms, with a social convention for precisely differentiating them, could in and of itself be an important addition to the Web. If you and I decide that we will use the term “http://www.cs.rpi.edu/~hendler/elephant†to designate some particular entity, then it really doesn’t matter what the other blind men think it is, they won’t be confused when they use the natural language term “elephant†which is not even close, lexigraphically, to the longer term you and I are using. And if they choose to use their own URI, “http://www.other.blind.guys.org/elephant†it won’t get confused with ours.
Too right! I paraphrase this in my RDF tutorial as Don’t use my names for your ideas, unless you mean to refer the exact same thing. Then please do!. This Wittgenstein avoidance technique was a stroke of genius: the person who creates the name gets to define it and the definitions can be in terms of other names. Anyone wanting to talk about the same thing can check the definition and if they agree with it they should feel free to use that name, if not then they can just create their own. Because there’s this way to define names in terms of one another then every new name created can potentially be related to any other. This can even be done for private interpretations of concepts that one person may consider to be close enough for their own purposes. If I want to say “cricket” and “chess” are both “games” then I can do so for my own purposes, even if other people consider one to be a “sport” and the other a “pastime”
The second key innovation that TBL made that Jim doesn’t refer to is the selection of URI syntax for the names. Arguably this is actually the more important innovation since without it the earlier unique naming technique cannot work in practice. URIs have the important property of dereferenceability which means that they can be used to fetch information about the thing the name represents. We see this every day when we type URIs starting with http:// into our web browsers. For names that someone has created to represent concepts like cricket it’s useful to send the definition when the URI is accessed. That way the user can decide whether they want to use that name for their own conversations. The use of URIs for naming is what makes the Semantic Web the Semantic Web
Actually, I should probably have been clearer in my mail — I wasn’t involved in the early RDF days – but I’ve been told on occasion that the URI stuff was Tim’s primary input to some of that (see his “webize” article at http://www.w3.org/DesignIssues/Webize) and a lot of the RDF model and syntax work was done before he really got seriously involved w/the RDF efforts. In the blog piece you’re responding to, you’ll notice I blurred the URI/RDF issues, but you are right that that was a key innovation. I don’t know who had the idea of putting dereferencible machine-readable documents at these URIs either – we had that in SHOE, and I remember that we were using it about the time RDF came out with that design, but I have no clue where that “meme” actually involved – I do know it was in the mid-90s (SHOE was published in 95 w/a URI model) so there’s a lot of room for historical revisionism :-) -JH