[cap-talk] Limiting case considered (was: Re: Selling capabilities programming)

[Karp, Alan H]

Jed wrote:
> 
> Hmmm.  I don't understand the above "negative permission".  Do you
> think it's relevant to this considered "limiting case" - i.e.
> the case where all communication of permissions is done via
> proxying?
> 
How does the proxy know whether or not to block a particular request?
There must be something about the requester that makes an otherwise
legitimate right invalid.  In Client Utility, we used the same kind of
capability that enabled some rights to make others invalid.  Hence, the
term negative capability.  An alternative would be to use a caretaker
with an administrator having the revoke privilege.  I would not call
that a negative capability, but the effect is the same.

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Alan Karp
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