digraph G {
a -> {x y z}
b -> {x y z}
c -> {x y z}
}
Suppose we have two components-- X and Y-- which depend on two other lower-level components-- A and B. How would you draw this as a block dependency diagram without repetition?
If both X and Y depend on B, then X and Y must be above B, and both touch B. If X and Y are orthogonal rectangles, then the entire X-Y edge is obscured from below. This means that another lower-level component A must can only interact with either X or Y. You'd need to allow X or Y to no longer be orthogonal rectangles to overcome this, or need to give up on the vertical organization of dependencies.