Brad Fitzpatrick and David Recordon recently wrote an interesting paper Thoughts on the Social Graph which gathered quite a lot of attention. They addressed some themes which I’ve been thinking about for quite a while now, and certainly moved the issue on a lot more than the recent Wired article did.

There’s no doubt that Brad & David know what they are talking about, either. Indeed, if Tim O’Reilly invented Web 2.0, then I think it’s not much of an exaggeration to say that Brad wrote the software which powers it.

However, I think their approach to the social network problem is surprising. In particular, I think it’s odd that the people who invented OpenID are proposing a centralized repository for all social networking data.

I believe there are better approaches. I’ve proposed and built a demonstrator for a system using what must be one of the most under appreciated data structures of all time: the Bloom filter. In short, a Bloom filter is a compact data structure which will remember if it has seen a piece of data previously, without remember the data itself. Obviously, this is useful in the social networking context because you can do things like load up all a users contact and then make the Bloom filter public. That allows system to query the filter to see if they know another user, without exposing their contact list to privacy leaks.

Incidentally, that demonstrator is my first Facebook app. Writing Facebook apps turns out to be pretty nice, although in this case I wrote it in PHP -which is less enjoyable. Have I ever mentioned that I’m not a huge PHP fan? Perhaps that’s partially because I don’t know PHP at all, but it’s just such a goopy language. Mucking around with Ruby (which I don’t know either) makes you go hmmm.. that’s nice. Even in Javascript I find myself going hmm… okay.. not quite what I expected, but it kind of makes sense. Doing the same in PHP just makes you go hmmm… – not in a good way, either.