I stand in the position of OS implementor, and so have the authority to do anything I want... :-)
More seriously, we can separate the traversal (the "mark" pass) from the inquiry. The authority to traverse needs to be closely held indeed. We can, however, imagine a number of relatively safe questions that the traversal agent can elect to answer. The two seem readily separated.
Bill Frantz <firstname.lastname@example.org> on 12/23/98 04:07:27 PM
To: Jonathan S Shapiro/Watson/IBM, email@example.com
Subject: Re: GC & sensory pointers.
At 01:49 PM 12/23/98 -0500, firstname.lastname@example.org wrote: Sensory keys do produce an interesting problem for trying to answer what I think is the really important question. The GC form is, where has all my storage gone? The zap form is, if I zap this object, what will break? Where do you stand to have enough authority to answer these questions?