I have the following situation:

I'm developing an add-in for a UML modeling tool. The models that can be created by the user are stored inside the main application and a limited access to the models is given through its API. However, the add-in has a lot of callbacks for events that are triggered by the main application, when changes to the model occur by the user. Since the models are already stored once in the main application, I considered it not practicable to duplicate the models in the add-in, which leads to the fact that I have only behavior in the add-in, rather than having a state.

This behavior is mainly expressed by static functions, that are organized in functional cohesive classes. The callbacks for the events have always references to the model elements relevant for the specifc event that ocurred.

First, it seemed to me that this is a procedural style in general, but procedural style doesn't consider events/callbacks, so this boils down to the question.

How is this programming style called?