[E-Lang] New Page: Partially Ordered Message Delivery

Karp, Alan alan_karp@hp.com
Wed, 14 Feb 2001 09:10:05 -0800

> -----Original Message-----
> From: Tyler Close [mailto:tclose@oilspace.com]
> Sent: Wednesday, February 14, 2001 3:15 AM
> To: Mark S. Miller
> Cc: E Language Discussions
> Subject: RE: [E-Lang] New Page: Partially Ordered Message Delivery
> In E, the Carol reference is bound to the lifetime of the connection
> that was started as a result of the liveRef() call on srBob. When this
> connection dies, the E Carol reference gets smashed. In Droplets, the
> Carol reference is just another sturdy reference that lives for as
> long as the Bob Vat is willing to let it live. This makes surviving
> temporary partitions a lot easier.

When designing e-speak, we saw value in both situations.  There are times
when the normal behavior is for the connection to exist, such as the two
machines on my desk.  There are other times when the normal behavior is for
there to be no connection, such as people browsing my web site.  

We decided that it should be a policy decision based on who you're talking
to as to which behavior you got.  Where we expected the connection to be
there, all references were kept and were immediately available on
reconnection.  Where the connection was ad hoc, the references were thrown
away when the connection was lost and had to be rebuilt if the machines
reconnected.  We also discussed a continuum of policies based on leases but
decided to stay with two modes of operation until we saw a need for more

Alan Karp
Principal Scientist
Decision Technology Department
Hewlett-Packard Laboratories MS 1U-2
1501 Page Mill Road
Palo Alto, CA 94304
(650) 857-3967, fax (650) 857-6278