Adding behavior to an action vs adding a sub-diagram

Question

I am using visual paradigm community edition UML tool. And I am creating an activity diagram with some actions in it. I noticed that there is an option when you right click an action saying : "Behavior" and it leads to another menu which enables me to add diagrams to that behavior. And there is another option to add a sub-diagram. Now a sub-diagram is a diagram that is executed or run when the parent diagram gets invoked. What I do not know is, what is that behavior option and how is different from the sub-diagram option?

Answer 1

I am not familiar with your UML tool, but according to UML standard, Activity Diagram may depict only part of the whole activity. Generally activities may be very complicated and expressed using multiple diagrams. Activity is executed from Initial Node to Activity Final node. All Actions in between may execute any behaviors or any other activities. Diagrams are used only to represent the inner parts of the activity.

I hope this is not too messy answer.

Answer 2

I sent an email to the support team of the visual paradigm tool. This is the reply I received on the matter :

"The sub-diagram and behavior are having 2 different meaning. The sub-diagram is a general feature for drill down an model model to elaborate its details, it is supported for all the model types. The behavior is something specially defined according to the UML specification, which is used to explain the details of the action. So you can consider the behavior is something specific for action for defining its details, while the sub-diagram is a general purpose feature."

I just wanted to share this with everyone here in case someone was wondering.