[Squeak-e] Re: [e-lang] Re: Croquet, Unum questions

[Mark Miller]

On 2004, Jul 24, , at 19:05, Mark Miller wrote:
>[...] Several of us were distracted, in a major way, this
>week. More about that soon...

We were distracted by an invitation-only workshop, held at HP Labs, focused 
on exploring future possibilities for Croquet. 
http://chess.eecs.berkeley.edu/croquet/ is a start on a website resulting 
from this workshop. The workshop was organized by Rick McGeer and attended 
by about 30 people, including 
* three of the main Croquet architects (David Smith, David Reed, and Andreas Raab), 
* several other Croquet-ers (Mark McCahill, Julian Lombardi) 
* and Squeakers (Dan Ingalls, Ted Keahler, Lex Spoon, Anthony Hannan, Ian Piumarta, Scott Wallace), 
* several members of the e-lang community (Chip Morningstar, Kevin Reid, Ka-Ping Yee, Marc Stiegler, Alan Karp, Tyler Close, Dean Tribble, and myself), 
* George Bosworth of Digitalk Smalltalk and .NET CLR fame, 
* Robert Adams of Intel and PlanetLab,
* and Prof. Edward Lee of Berkeley.
* (and probably some others I forgot)


The Electric Communities and e-lang perspectives were represented well, and 
played well with other perspectives that were presented. I think the 
lessons from our perspectives were taken to heart, and their relevance to 
the Croquet undertaking were clear. Actually, I think I'm way understating 
the case, but I'll wait to see what others have to say.

In any case, I think it's fair to say that we have consensus on using 
object-capability security as the underlying security mechanism, on top of 
which Croquet's security architecture should be built. And that we have 
consensus that "Threads are evil" -- that the conventional (shared memory 
multithreading & fine-grained locking) paradigm of concurrency is
unworkable, and that instead, time should proceed according to a partial 
causal order among events, where each event is the deterministic execution 
of a sequential program to completion. (E and Croquet already have this 
perspective in common, but with some interesting differences.)


I have asked the Croquet architects to evaluate the suitability of the 
Kernel-E virtual machine definition as a proposed foundation on which 
Croquet should be reconstructed. They are currently evaluating it. If 
adopted, the plan would probably be to start by completing Dean's 
E-on-Squeak effort in the short term, and do a more direct implementation of 
Kernel-E on their virtual machine infrastructure in the long term. 




At 04:05 PM 7/28/2004  Wednesday, Kevin Reid wrote:
>>(Note: the picture painted here doesn't yet cover the case where there are
>>potentially multiple authoritative presences. I now think I like Dean's
>>proposal for that better than Uni-Tea
>>http://www.erights.org/talks/uni-tea/index.html .
>
>I don't recall or never heard what Dean's proposal was.

In the Uni-Tea proposal, we map a Tea Party to an Unum, and make the 
replication of authoritative presences be a generalization of presence 
spread among vats. Dean suggests that, instead, we map a Tea Party to a 
virtual vat, and implement fault tolerant replicated vats. Then, at the vat 
level of abstraction, an individual Unum would still just have one 
authoritative presence, permanently tied to its virtual vat of origin. 
Rather than making the replication, consensus, and fault tolerance protocols 
be Unum design choices, we should make these choices when instantiating a 
fault-tolerant replicated vat. In Dean's proposal, it is especially clear 
that you only do fault tolerant replication among sites mutually trusted to 
try to run their replicas correctly, since that vat's private key would be 
replicated at all those sites.


-- 
Text by me above is hereby placed in the public domain

        Cheers,
        --MarkM