Re: [friam] What is a capability?

My definition covers both ocap languages and ocap operating systems,
especially the KeyKOS family. I would be very surprised if it does not
cover seL4, but I haven't investigated.

See especially Table 9.1: "Capability / OS / Object corresponding
concepts". It is intended as a kind of rosetta stone, translating between
different communities' different names for the same concepts. Section 9.1
talks each concept through with both language and OS examples.

It *almost* covers distributed cryptographic caps, but for the ways in
which these must be weaker than ocaps (which Carl just alluded to). Section
11.5 attempts to clarify these differences.

(Alan, see also the last paragraph of 11.5.2, inserted specially for you,
explaining that intermediate case between ocap and cryptocaps that you drew
to my attention.)




On Thu, Jan 8, 2015 at 3:58 PM, Mike Stay <[email protected]> wrote:

> [+ cap-talk]
> On Thu, Jan 8, 2015 at 3:44 PM, Carl Hewitt <[email protected]> wrote:
> > Alan,
> >
> > Thanks!
> >
> > But exactly what *is* a capability?  And *exactly* how can a capability
> be used?
>
> I think that question presupposes a bunch of other stuff.  It's rather
> like asking "What is a musical note?"  One could mean a vibration of a
> particular frequency, the pitch class, a mark on a page, or the qualia
> associated with perception of the note.
>
> Mark Miller defined object capabilities in the context of an
> ocap-secure programming language; in that context, it is an object
> reference.  If you add ambient authority to the language such that it
> is no longer ocap-secure, the reference is no longer an object
> capability.
> --
> Mike Stay - [email protected]
> http://www.cs.auckland.ac.nz/~mike
> http://reperiendi.wordpress.com
>
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-- 
    Cheers,
    --MarkM

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