Composition and other topics

[Jonathan Shapiro]

   Offhand I can't think of any compelling uses of composed mappings
   outside of facilitating memory sharing.  I think the memory sharing
   argument is compelling enough by itself to warrant support for
   composed mappings if implementation complexity is reasonable,
   but I'll admit that composed mappings are probably not the ideal way
   to implement other things that have to play with the actual data
   backed by a mapping.

Given my comments about different page sizes earlier today, what do
you propose as the minimum unit of composition, and what rules would
you propose for composing authorities to produce a page-level
protection?

Jonathan