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

[Bill Frantz]

alan.karp at hp.com (Karp, Alan H) on Wednesday, January 28, 2009 wrote:

>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?

I think, in the case of CapTP (the part of the E implementation which is
responsible for transferring capabilities over connections), that the
reference to Carol Bob receives from Alice will look different from the one
he already has until the three-party handoff completes. Any kind of EQ
operation on the capabilities will also have to wait for the three-party
handoff. So, Bob will not know they are the same reference until the E
ordering guarantee has, in fact, been met.

MarkM?  Kevin?

Cheers - Bill

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