A is a start point, B is the end point. X is the process or change. Note that just having scope doesn't mean that the scope isn't too large. To narrow scope give more information or ask for less, as appropriate.
a) I have A and X, give me B (cool, *requires* narrow scope on B)
b) I have B and X, give me A (cool, scope is normally always implied by describing the outcome)
c) I have X, give me A and B (Too broad, scope is by defintion undefined) (See hack the universe pre edits)
d) I have A and B, give me X (requies some kind of scope (often on X) and is normally always implicit on the other)