Thank you Satomi,
I am developing a plugin to automatically check refinements of behavioural UML models, starting with sequence diagrams. In fact, I am having a problem right now related to external libs that should be used by the plugin. I have inserted the dependencies in the pom.xml using the "system" scope. However, when I lauch the plugin, Astah doesn't seem to be loading the library (a jar file) that I have declared because the console shows a ClassNotFoundException of a class belonging to this specific library. Do you have any idea on how to solve this issue?