I was explaining the PostgreSQL version naming convention to my colleague a couple of days ago. The differences between e.g. 8.3 and 8.4 and what is different between 8.4 and 9.0 and what should be used during database migration to another version. I knew all that just because somebody told me that many years ago (I think it was depesz – thanks).
However I was unaware that there is documentation of the whole versioning issue. All you can find here.
Another reason why love this project. And yes, you should have that versioning policy in you project too (it really doesn’t matter if it looks different – better to have a convention than not).