some basic questions

Klacke <>
Mon Oct 11 10:20:17 CEST 1999


Michael Skowronski writes:
 > 
 > i believe, the same group is working on a new toolkit called Ensemble.
 > from what i understand, the ISIS toolkit took a ``monolithic'' type
 > approach and offered pre-defined and limited choices as to ordering and
 > membership -- Ensemble i think has a sort of an OO approach and is more
 > open, extensible and composible.  have you had a look at Ensemble?  
 > 

Yes, we looked a lot at the Ensemble architecture as well
during the ISIS/Erlang project. Ensemble is a very nice system
written by Marc Hayden while at Cornell. He has now quit there 
and started at Compaq, doing other things. I met Marc Hayden at
a conference last year and we discussed Erlang/ML/isis/Ensemble.

Ensemble reimplements the ISIS protocolls. It's all written in
ML !!!. Ensemble is really interesting from an Erlang point of view 
as well, not so much for it's ISIS implementation as for *how*
it's implemented. Marc did a really cool thing with micro layers
of protocols. 

Different layers could then be stacked on top of each
other in different ways. (Note that this is in complete contrast 
to how protocols are normally *implemented*  where
typically all the layers are completelet intertwined for efficency 
reasons). Well, after the layer stacking, a cool type/proof/reduction
machinery was run on the protocol stack which produced a specialized
stack. A bit like compiler unfolding. The net result was a really
efficent protocol implementaion.

Ensemble was finished a couple of years ago and I don't know
if it's actively maintained any more since Marc quit Cornell.


 >  
 > > However, I still think that we need better abstractions than
 > > the ones we have today in order to build distributed apps.
 > 
 > yes, i agree.

I think that the group concept from ISIS was/is a really nice attempt
at finding better distributed apps abstractions, however using them
and using them good maybe isn't as easy as it should be. 

Cheers

/klacke
Claes Wikström                          Tel: +46 (0)8 692 22 09
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