[cap-talk] Selling capabilities programming

[Marcus Brinkmann]

At Thu, 26 Jul 2007 17:30:43 -0000,
"Karp, Alan H" <alan.karp at hp.com> wrote:
> 
> Marcus Brinkmann wrote:
> > 
> > I don't think that's quite correct.  Usually either semantic can be
> > emulated with the other.  To emulate map semantics in a copy model,
> > you create a wrapper process for each capability.
> > 
> Who does the emulation?  Alice can pass the bits representing the
> capability to Bob.  Hence, Bob and Alice use the same bits.  That means
> you can't remove the capability Alice uses when her process ends without
> removing Bob's right.

This seems to be exactly what one wants (in either model).  Can you
clarify what you would expect to happen instead?  Note that map
semantics imply recursive unmap.

In a system with only copy semantics, the party doing the delegation
can decide to create and delegate a wrapper instead to achieve map
semantics for this one delegation.

In a system with only map semantics, achieving copy semantics (again,
for one delegation) requires the cooperation of the provider of the
capability and a three-way transaction.

Thanks,
Marcus