I am by no means a UML guru, however I do believe that UML can help me communicate complex ideas.  In order for this communication of ideas to be useful everyone taking part in the conversation needs to be speaking the same language, but don't panic, not everyone taking part in the conversation needs to be fluent.  

I was recently writing a TCP connector for MySQL so that I could call it from both 64-bit LabVIEW and LabVIEW RT and I realized that I needed a way to spy on my localhost network traffic for debug purposes.  So I fired up WireShark, but it turns out that WireShark can't see localhost traffic because localhost traffic is not sent over a real network interface.

As writers of software we strive to craft code with high cohesion and loose coupling.  This can be tough to do with the Actor Framework as the default method of sending messages between actors effectively couples them together.  Depending on your application this coupling may not matter, but I will show you one way to manage it if it does.

The above image illustrates a small section of the flow of control for an application used to calculate properties of a black hole.  There is a high level module used to calculate the tidal force that objects experience while near a black hole's event horizon.  This tidal force calculation requires the black hole's mass as an input, which is calculated by a lower level module.  The high level tidal force module needs the black hole's mass in order to perform its calculation, and it depends on the low level mass module to supply it.