[cap-talk] Petnames versus E-order with ocaps

[Karp, Alan H]

E-order guarantees the following property.  If Alice sends a message to Carol, and then Alice sends a message to Bob containing a reference to Carol, and Bob uses that reference to send a message to Carol, Carol will receive the message from Bob after she receives the message from Alice.  (Did I get that right, MarkM?)  That ordering is not guaranteed if Bob sends a message to Carol using a reference not obtained from Alice.

A petname is a one-to-one mapping between an object reference and a name binding.  If Bob has a reference to Carol that he calls foo, a reference to Carol that Bob receives from Alice will also be denoted foo.

Here's where the versus comes in.  Bob would like to ensure that a message he sends to Carol arrives after any messages Alice sent to Carol before she sent Bob a reference to Carol.  In a petname system, he can't do that if he had a reference to Carol before Alice sent him one.  Is that a problem or a feature?

________________________
Alan Karp
Principal Scientist
Virus Safe Computing Initiative
Hewlett-Packard Laboratories
1501 Page Mill Road
Palo Alto, CA 94304
(650) 857-3967, fax (650) 857-7029
http://www.hpl.hp.com/personal/Alan_Karp