Transactive Memory

I've been doing some research on Software Transactional Memory recently and as a result started to read about Transactive Memory. Now it quickly became apparent that the two things are unrelated, but I found transactive memory to be very interesting (not to indicate that STM isn't interesting!) Put simply, transactive memory is the name for the process whereby people selectively remember things and rely on their relationships with other people, or other things, to remember everything else. So for example, you don't remember every single phone number for everyone you know: you're selective (because that's how the brain works) and remember the "top" 6 or 7, but will probably rely on a telephone book or a PDA for the others. In the home, you may not remember how all of your friends are related to one another, maybe relying on your partner to do that. If you are a technophobe then you may rely on someone in your family to program the DVD player so you don't have to remember how to do it. If you've got kids then you may rely on your partner to do the bulk of their welfare. And the list goes on.

So what has this to do with STM? Well as I said at the start, absolutely nothing. But it does have relevancy to something else I've been interested in for the past few years: repositories. I've always believed that systems such as repositories are better implemented in a federated manner: they scale much better. This means that although you may have a logical notion of a repository, each physical instance is responsible for some different aspect(s) of the whole "mind". This is important because, for example, how you store and index service binaries is different to how you would store and index service contracts, or workflow definitions etc. In this kind of set up if you ask one repository instance "do you know about X" it should say either "no, but I know a man who does" or "no, but hold on and I'll get the answer for you". I'd never been able to put a name to the approach (beyond federation), but it seems to me that this is precisely transitive memory from a software system. DNS works in the same way.