Illustrating the message path in documentation

[Dar Scott]

What is the traditional imagery (or a preferred imagery) for picturing 
message paths?

Much of the documentation refers to "along" the path or "the next 
object" in the path or "traversing" the path or "passed on through" the 
path or "continue along" the path or "further" in the path, or "after" 
or "before".  This seems like it would give me lots of freedom in 
illustrating this.

However, I think I have seen references to "up the path", or often 
"higher level" when referring to further along the path.  (This is 
contrary to my imagination which has messages "falling" and bumping into 
handlers in objects on the way down, some sent messages continuing into 
the bottomless pit.)  I suppose "up" could be read further along, but 
the "higher level" may say otherwise.

The "insert script" command refers to "front" and "back".  I think this 
can be read both in the sense of close and near and in the sense of a 
chain (see "after" and "before" above).

In the past I would diagram libraries below the modules that use those.  
Is this right for Revolution?

What's the "right" way to diagram objects and their path relationships?

Dar Scott