Persistence and dereferenceability

[31 March 2009]

My esteemed former colleague Thomas Roessler has posted a musing on the fragility of the electronic historical record and the difficulties of achieving persistence, when companies go out of existence and coincidentally stop maintaining their Web sites or paying their domain registration fees.

After reading Thomas’s post, my evil twin Enrique came close to throwing a temper tantrum. (Actually, that’s quite unfair. For Enrique, he was remarkably well behaved.)

“The semantic web partisans,” he shouted, “have spent the last ten years or more telling us that URLs are the perfect naming mechanism: a single, integrated space of names with distributed naming authority. Haven’t they?”

“Well,” I said, “strictly speaking, I think they have mostly been talking about URIs, for the last few years at least.” He ignored this.

“They have been telling us we should use URLs for naming absolutely everything. Including everything we care about. Including Aeschylus and Euripides! Homer! Sappho! Including Shelley, and Keats, and Pope!”

I couldn’t help starting to hum ‘Brush up your Shakespeare’ at this, but he ignored me. This in itself was unusual; he is usually a sucker for Cole Porter. I guess he really was kind of worked up.

“And when anyone expressed concern about (a) the fact that the power to mint URLs is tied up with the regular payment of fees, so it’s really not equally accessible to everyone, or (b) the possibility that URLs don’t have the kind of longevity needed for real persistence, they just told us again, louder, that we should be using URLs for everything.”

“Now, don’t bring up URNs!” I told him, in a warning tone. “We don’t want to open those old wounds again, do we?”

“And why the hell not?” he roared. “What do the SemWeb people think they are playing at?!”

“Well,” I said.

“Either they are surprised at this problem, in which case you have to ask: ‘How can they be surprised? What kind of idiots must they be not to have seen this coming?’“

“Well,” I said.

“Or else they aren’t surprised, in which case you have to ask what they are smoking! Is it their attention span so short that it has never occurred to them that names sometimes need to last for longer than Netscape, Inc., happens to be in business?”

“Well,” I said. I realized I didn’t really have a good answer.

“And you?!” he snarled, turning on me and grabbing my lapels. “You were there for years — you couldn’t take a moment to point out to them that a naming convention can be used for everything we care about only if it can be used for the monuments of human culture? You couldn’t be bothered to point out that URLs can be suitable for naming parts of our cultural heritage only if they can last for a few hundred, preferably a few tens of thousands, of years? What use are you?!”

“Well,” I said.

“What use are URLs and their much hyped dereferenceability, if they can break this fast?”

“Well,” I said.

Long pause.

I am not sure Enrique’s complaints are entirely fair, but I also didn’t know how to answer them. I fear he is still waiting for an answer.