Near the end of the talk someone asks you how to delete data if the state of the machine is just a function of the network packets it has received.

I have to admit I didn't really understand your answer:

> [When you try to forget data] you're making a subset of this computer that will not compute when it tries to use this information.

Could you elaborate a little on what that means, and how you'd apply it in practice. If I wanted to not just make data inaccessible but actually purge it from my machine, how would I do so?

So, you're doing exactly the same thing when you press ^C on an event - what happens is, the event fails to compute. It doesn't go into your log. It doesn't affect your state. It never happened. Packet caused an infinite loop? You never got that packet. And so on.

If an event depends on data that's been deleted, that event never happened. But, at the Unix level (which can generate any events it wants), we can generate another event which reports the error. So it's not like things fall silently down the hole, either. (For the same reason, you can also get the stack trace of the infinite loop that was interrupted by your ^C.)