[cap-talk] Is EQ necessary for PetName systems?

[Jed Donnelley]

At 05:01 AM 10/19/2007, Jonathan S. Shapiro wrote:
>There is one case where EQ appears to be necessary. This has nothing to
>do with pet names.
>
>In KeyKOS/EROS, invoking a resume capability destroys it. In such
>systems, there must be some comparator operation that can compare two
>capabilities for equality without invoking the capabilities.
>
>I am being deliberately ambiguous concerning what is meant by equality.
>the point is simply that primitive equality-like operations cannot be
>implemented by the objects in system having the "destroy on use"
>property.

Hmmm.  It need not be the object itself that is invoked.
E.g. I can pass two capabilities to some other object and
ask if they are "EQ".  The weaker "MyCap" primitive is
along these lines in that you invoke your extension
capability and pass it a capability that you want
to ask whether it is one of yours (and if so which).
You don't have to invoke the capability itself to
ask "MyCap?".

This may just move the problem down a level, but it
seems to me that such abstraction and the opportunity
to only invoke capabilities at the "user" level
might be important.

--Jed  http://www.webstart.com/jed/