I use class diagrams for a long time to think and make planification and now I use Activity diagrams to help me refactoring in my code which beginning to be complex (for the GUI system).
I find them very useful !
P.S. I didn”t know where to write this message so I choosed the Teaching category. A “other” acteory would be ok I think
interesting!
Can you explain where to download your uml tool and how to use it?
don’t have to much time just now (I’ll come back to it). 
Violet is here :
P.S. It is quite simple to use.
You may read a file with a browser, you need to open it with Violet to edit.
look at the file html to see how he is doing it :))
About a week ago, Violet UML Editor stopped working due to an increase in Java security.
Violet Uml Editor starts with a jar file and only “signed” jars are accepted now…
So, I searched for another software on the off chance and I came across an even more convenient UML editor.
UMLet: the interface is completely different and at first glance more rustic, but if you use it, you realize that the software is even better than Violet Editor.
It works on Linux, Mac and Windows and there is even a version that works in browsers!!!
P.S. I love software that does only one thing and does it very well!
It’s GNU ! 