On Mon, Jun 13, 2011 at 11:17 AM, Alan Kay <[email protected]> wrote:
> It would be great if everyone on this list would think deeply about how to > have an "eternal" system, and only be amplified by it. > > For example, take a look at Alex Warth's "Worlds" work (and paper) and see > how that might be used to deal with larger problems of consistency and > version control in a live system. > > I also believe that we should advance things so that there are no hidden > dependencies, and that dependencies are nailed semantically. > Alan/Alex, Worlds does not address how to debug a live system other than random state-space exploration. Have you made progress I am not aware of? As I've said before, computer scientists must be much better at studying living systems if they want to build systems that can function at scales that exceed the capacity for humans to configure it. How exactly does "Worlds" truly deal with larger problems of consistency and version control? The same question applies to David Reed's TeaTime, which is really just Worlds with an illusion of infinite memory. I, too, could edit a PhotoShop image forever and scroll through the history of every edit I ever made using the History view, but I would need a lot of memory to do it. In practice, PhotoShop requires the user to do things like compacting layers and other memory organization techniques. To really make something like TeaTime or Worlds useful, you need bounds on how the history relation of a program affects the input/output relation. Even with bounds, you can still have "glitches" like the Brock/Ackerman Anomaly. But the nice thing about bounds is there is a lot of mathematical ways you can describe bounds, such as linear temporal logic or linear types or just any linearity guarantee period. That said, it is okay to have hidden dependencies, as long as somebody is allowed to check those dependencies at any point in time they please. A bad hidden dependency would be something like a NAT firewall causing a protocol to stop working. But an even more pernicious hidden dependency is in all software: BUGS! Dealing with bugs has led Carl Hewitt to propose we should just live with them, and reason about live systems using inconsistency tolerant logic. He prefers his own logic, DirectLogic. Cheers, Z-Bo
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