One thing I actually knew about Wikipedia

I see Wikipedia has snuck a little "Ten things you didn't know about Wikipedia" link onto their pages (now that's not very NPOV, is it? [Ed. Note: It's since been softened to "Ten things you may not know ..."]). The sleeper in the list is #4: "You cannot actually change anything in Wikipedia... (you can only add to it)".

This feature of Wikis, dating back to the original WikiWikiWeb, is what gives them their agility. Since there's a complete history, there's an "undo" button on everything. This lets editors "be bold", makes it easy to revert vandalism, provides a fascinating view of the process behind a wiki apart from the results, and doubtless provides any number of other benefits I haven't thought of.

I've long been convinced that this sort of "change by adding" model is the norm in the non-virtual world, or at least closer to the norm than the "instant, compete overwrite" model that the CPU sees. Some random examples:

• If you return an item, the charge doesn't disappear from your account. Instead, a matching credit appears.
• Other recordkeeping -- school transcripts, employment records, hospital charts, etc. -- tend to follow a similar pattern. Your state changes and the record maintains a history, adding new notations and documents as things happen.
  
• A print newspaper, by necessity, can't unprint an article. Instead, it issues a correction or retraction.
• Similarly, reference books accrue addenda and errata. When these are finally published in a new edition, the previous edition still exists.

These same patterns appear on the web, as well, but there is also the option of keeping only the current state. An online news source may issue a correction but will often quietly update the referenced article as it does so. For that matter, I'm free to edit any post on this blog after the fact (and I occasionally will).

Web protocols handle either scenario. It's up to the author to decide whether a link means something ephemeral or something permanent. Thus the distinction between permalink, which implies that the contents will not change, and plain link, which carries no particular implication.

There is a full spectrum of mutability available, from a true permalink from a source like Wikipedia that promises no changes absent a full-blown catastrophe, to something completely ephemeral like the wind speed at a given weather station. There is also a lot of interesting territory in between that seems worth exploring.