Hi,
As you may know, it's possible to "talk to" a website like Facebook, and that's how games such as Farmville have been built - I was wanting to know how this is architected, i.e. how does a website decide how to "offer up" its data to the outside world?

I'd like your favourite web links, or even paper book recommendations, though I don't if those will be available or affordable over here, or, what would be especially great would be Video lectures, maybe on Youtube?

Thanks very much, I hope this generates a stimulating discussion.

My question is about *general* software architecture, not Facebook in particular.
i.e. how would I do it on MY site? don't wanna copy Facebook, do I?

Some sites provide API's which can be used in various programming languages. I think ebay does it (or it certainly used to if not anymore).