John DiMarco on Computing (and occasionally other things)
I welcome comments by email to jdd at cs.toronto.edu.

Fri 03 Dec 2010 21:52

What's right about ikiwiki?
Chris Siebenmann pointed me today at ikiwiki. It's a wiki that can also function as a blog. It's potentially interesting, he said. And he was right: to me, it seems definitely interesting. I've only started looking at it, but there's something about it that I like very much, something it does right that most web 2.0 applications seem to do wrong: ikiwiki uses the right sort of tool to store the wiki text. What's the right tool? In my opinion, it's a revision control system (well, to be more exact, a filesystem coupled with a revision control system).

Why is this the right tool? Well, what's wiki data? It's a collection of edited text documents. Databases, such as those used by most wikis and blogs, are designed for large collections of data records, not documents. Yes, they can handle documents, but using them for a collection of documents is like using a tractor-trailer for a trip to the beach. Yes, you can do it, but it's a bit excessive, and you may end up stuck in the sand. On the contrary, it seems to me that a filesystem, not a database, is the appropriate tool for document storage, and a revision control system, not a database, is the tool of choice to keep track of document edits.

Then why do so many wiki and blog implementations use databases such as mysql or postgres as their back-end? I don't know. I suspect it's a lack of imagination: when you're holding a hammer, everything looks like a nail. In fact, "lite" versions of these databases (e.g. sqllite) have been created to take advantage of the fact that the full power of these database systems are not needed by many systems that use them. But "lite" databases for wiki/blog back-ends seem to me to be like cardboard tractor-trailers: still the wrong tool, but with some of the overkill stripped out.

Even more to ikiwiki's credit than the fact that it has what I think is the right sort of backend, it also allows you to use a wide array of different revision control systems (svn, git, cvs, mercurial, etc.), or even no revision control system at all. I like this. Revision control systems seem to be a matter of widely varying preference, and ikiwiki's agnosticism in this regard makes it appealing to a wider array of users.

I've only started looking at ikiwiki, and it may be that in the end, I'll decide I don't like it for some reason or another, but whether I end up liking it or not, or whether we use it or not, I think ikiwiki is right in using a revision control system instead of a database for its backend. I wish it were not so rare in this respect.

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