Taxonomy of Facets & Composites
Mark S. Miller
Mon, 31 Jul 2000 11:02:30 -0700
>a) at least the local naming perspective of the lambda
>calculus, which is shared by the treatment of clist indexes in capability
At 08:51 AM 7/31/00 , Tyler Close wrote:
>E the language is just a way of expressing compositions of the
>Granovetter operator. Is it reasonable to expect that if we can
>understand all capability systems in terms of the Granovetter operator
>that E the language could be used to script them? If so, then the
>style of the E language (lexical scoping) does not belong in a
>taxonomy of capability systems, since it could be applied to all
>capability systems. Perhaps a second taxonomy of 'Granovetter
By "local naming perspective of the lambda calculus", I mean something less
than full lexical scoping, as I hoped my inclusion of clist indexes would
indicate. I would also claim that my Pet Name Markup Language proposal
http://www.erights.org/elib/capability/pnml.html shares this "perspective",
even though its particulars are very different from the first two. What is
this perspective? http://www.mediacity.com/~norm/CapTheory/NaP.html isn't a
bad start at stating it.
>I don't get b)? Has it escaped from your head yet?
No. But in the meantime, we've got three very clear examples represented
clearly by at least seven systems.
Sorry to be so vague, using perspectives and examples rather than formal
models. Such is the stuff of the conversations that eventually lead to
formal models. Once again, perhaps we should simply be using Hewitt's
Actors work rather than trying to reinvent it. Perhaps all capability
systems are security-equivalent to Actors. Actors have the Granovetter
nature, the lambda naming perspective, and a local side effects semantics
adequate to model all the others in a security-equivalent way. CLPs are
also a plausible choice of formal foundation, but they seem more complicated
and less "foundational" to me. Perhaps this is a matter of taste.
(Note: As a foundational formal model of computation, I lump Kernel-Joule in
with Actors, though one may argue that it's yet a third model.)
Unfortunately, neither Actors nor CLPs are widely known formal models even
on this list. This is another reason to try informal restatements of the
important properties of capability systems in general.