segment composition

[Jonathan Shapiro]

   Not exactly. You must invoke the outermost keeper that could have been
   responsible for the fault. In your example, since segment A's keeper
   doesn't intend to play tricks with segment D, segment A has a read/write
   key to segment D. Therefore A isn't responsible for the fault. D is
   because D contains a read-only key.

That sounds like it works for write access faults.  Is there an
analogous trick that can be used for handling invalid data, or does
that really have to go all the way through the chain?

Jonathan