in RDF

Shadows on the Web

This is a quick note, inspired by the recent burst of posts passing through Planet RDF about RDF, WebArch and a second “shadow” Web. Actually it’s not about that thread at all, except to note that Ian Davis asks just the right kind of questions when thinking about the WebArch claim that the Web ships with a hardcoded, timeless and built-in ontology, carving up the Universe between “information resources” and “non-information resources”. Various Talis folk are heading towards Bristol this week, so I expect we’ll pick up this theme offline again shortly! (Various other Talis folk – I’m happy to be counted as Talis person, even if they choose the worst picture of me for their blog :).

Anyhow, I made my peace with the TAG’s http-range-14 resolution long ago, and prefer the status quo to a situation where “/”-terminated namespaces are treated as risky and broken (as was the case pre-2005). But RDFa brings the “#” WebArch mess back to the forefront, since RDF and HTML can be blended within the same environment. Perhaps – reluctantly – we do need to revisit this perma-thread one last time. But not today! All I wanted to write about right now is the “shadow” metaphor. It crops up in Ian’s posts, and he cites Rob McCool’s writings. Since I’m unequiped with an IEEE login, I’m unsure where the metaphor originated. Ian’s usage is in terms of RDF creating a redundant and secondary structure that ordinary Web users don’t engage with, ie. a “shadow of the real thing”. I’m not going to pursue that point here, except to say I have sympathies, but am not too worried. GRDDL, RDFa etc help.

Instead, I’m going to suggest that we recycle the metaphor, since (when turned on its head) it gives an interesting metaphorical account of what the SW is all about. Like all 1-line metaphorical explanations of complex systems, the real value comes in picking it apart, and seeing where it doesn’t quote hold:

‘Web documents are the shadows cast on the Web by things in the world.

What do I mean here? Perhaps this is just pretentious, I’m not sure :) Let’s go back to the beginnings of the SW effort to picture this. In 1994 TimBL gave a Plenary talk at the first International WWW Conference. Amongst other things, he announced the creation of W3C, and described the task ahead of us in the Semantic Web community. This was two years before we had PICS, and three years before the first RDF drafts. People were all excited about Mosaic, to help date this. But even then, the description was clear, and well illustrated in a series of cartoon diagrams, eg:

TimBL 1994 Web semantics diagram

I’ve always liked these diagrams, and the words that went with them.

So much so that when I had the luxury of my own EU project to play with, they got reworked for us by Liz Turner: we made postcards and tshirts, which Libby delighted in sending to countless semwebbers to say “thanks!”. Here’s the postcard version:

SWAD-Europe postcard

The basic idea is just that Web documents are not intrinsically interesting things; what’s interesting, generally, is what they’re about. Web users don’t generally care much about sequences of unicode characters or bytes; we care about what they mean in our real lives. The objects they’re about, the agreements they describe, the real-world relationships and claims they capture. There is a Web of relationships in the world, describable in countless ways by countless people, and the information we put into the Web is just a pale shadow of that.

The Web according to TimBL, back in ’94:

To a computer, then, the web is a flat, boring world devoid of meaning. This is a pity, as in fact documents on the web describe real objects and imaginary concepts, and give particular relationships between them. For example, a document might describe a person. The title document to a house describes a house and also the ownership relation with a person. [...]

On this thinking, Web documents are the secondary thing; the shadow. What matters is the world and it’s mapping into digital documents, rather than the digital stuff alone. The shadow metaphor breaks down a little, if you think of the light source as something like the Sun, ie. with each real-world entity shadowed by a single (authoritative?) document in the Web. Life’s not like that, and the Web’s not like that either. Objects and relationships in the real world show up in numerous ways on the Web; or sometimes (thankfully) not at all. If Web documents can be thought of as shadows, they’re shadows cast in many lights, many colours, and by multiple independent light sources. Some indistinct, soft and flattering; occasionally frustratingly vague. Others bright, harshly precise and rigorously scientific (and correspondingly expensive and experty to use). But the core story is that it’s the same shared world that we’re seeing in all these different lights, and that the Web and the world are both richer because life is illustrated from multiple perspectives, and because the results can be visible to all.

The Semantic Web is, on this story, not a shadow of the real Web, but a story about how the Web is a shadow of the world. The Semantic Web is, in fact, much more like a 1970s disco than a shadow…

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