editing and checking diagrammatic problems

Computer science frequently deals with graphical presentations of structures or behavior. Typical examples are trees, graphs, class diagrams, activity diagrams, finite automata, Petri nets, ...

Given a (family of) diagram editors, it is sufficient to associate two attributes "visible/invisible" and "correct/incorrect" with each node, connector, and label to allow educators to develop a diagram that students have to check for incorrect or missing diagram elements for a given problem. The diagram presented would only show visible elements, including incorrect ones to be deleted, while correct and invisible elements, which students need to add, would only exist in the shadow graph comprising all correct elements.

 Is anyone able to develop such a tool, maybe based on exiting open-source diagram editors?