Internet Alchemy

This is inspired by Jeni’s recent blog post What do URIs mean anyway? where she writes:

The imperfection of the real world as it applies to linked data is that URIs will be used in ambiguous ways. We might not like it; we might write best practice documents that encourage people to have separate URIs for web-thing and non-web-thing, develop tools that help people detect when they’ve used the wrong URI, and so on. But it will still happen, and in my opinion we need to work out how to cope.

I think there is less ambiguity than Jeni states.

A lot of the perception of ambiguity in these arguments comes from in-built preconceptions about the nature of documents on the web. It’s easy to forget that when you think you’re accessing a webpage you’re not really getting the actual document that is on the web server but just a kind of snapshot of it at a point in time. In HTTP we call those snapshots “representations”. The important point is that the URI always identifies the resource and never the representation. You use the representations to learn about the resource you are interacting with.

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Ambiguous references happen in the real world all the time. For example, the name Big Ben is used to refer to the clock tower and to the bell, but strictly speaking only one of those is right.

Most of the time these misplaced names don’t matter – listeners make assumptions about the intended referent and correct those assumptions as more information comes to light.

A lot of the time the possible referents share a lot of characteristics and can be used interchangeably. When giving directions you can say “head towards Big Ben” without fear of confusing people. You could even get away with “listen to the sound of Big Ben” because sound is perceived to come from a general location. The information a speaker produces Big Ben can be inconsistent for quite a long time before it becomes a problem.

But what happens when the speaker says something that crystallizes that inconsistency for the listener?

Suppose the speaker believes that Big Ben refers to the bell and the listener assumes it refers to the tower. The speaker suddenly says:

“Big Ben was cast in 1856 in Stockton-on-Tees”

The listener realizes now that they have been talking about different things.

“Oh, I thought you were talking about the tower”, the listener might exclaim.

“No, you ignoramous, the tower is called Victoria Tower. Big Ben is the bell inside it! How can a tower possibly be cast in a northern town?” retorts the speaker.

“Well, you learn something new every day,” says the listener ruefully.

Now the listener backtracks and applies all the information they had learned from the speaker about Bug Ben to the bell instead of the tower.

However, throughout this conversation neither the speaker nor the listener assumed the name Big Ben applied to two things at once. They both assumed it applied to a single referent, but they happened to be different ones. Once more information was shared then they managed to reach agreement on the actual referent for Big Ben.