I have a note about mappings and address spaces pending, but before I send it I want to ask a naive question about the map operations: Consider a sequence of operations in which A maps to B B maps same stuff to C. Is there some variant of the 'map' operation in which B does NOT retain the ability to revoke C's mapping? That is, in which the resulting mapping dependency hierarchy is A / \ B C instead of A | B | C That is, is there a way for a sender to give a receiver rights on data that are co-equal in all respects with those of the sender? If not, is it important? If such a "coequal map" operation existed, how often would it be used in contrast to the current map operation? shap -- Jonathan S. Shapiro <shap@eros-os.org>