Should GUI classes be included in class diagram in UML

Question

I need to develop a system for a library system from Java & Netbeans. I am wondering do I have to include classes made from Netbeans for user interfaces in the class diagram. In addition to that suppose we have a class "Librarian". I assume that I can create two classes one for UI and one that including details in the class diagram and use it in the UI class. Or I can implement, what class diagram says directly in the UI class for "Librarian". Please tell me which is the correct way that software engineers are supposed do.

Answer 1

Whether or not to show something in a class diagram depends on the intention of the editor and what he wants to show to his audience. Often it's a good idea to create overview diagrams where you omit details. The overview is then accompanied by a couple of detail diagrams which are logically oriented at sub-domains which in turn help to understand the systems as a whole.

Also it's not uncommon to just leave out "obvious" things. If you work with known scaffolds in certain domains you must not describe that again and agin but just can assume that it's known. In your case that would be the GUI part which will be known implicitly. You might consider to create a sketch of the scaffold somewhere in a more general class diagram. This could be helpful for people coming from other worlds (and not knowing NetBeans like me).

Beware of drawing wall-papers that contain each and every detail in a single class diagram. Looks impressive but is absolutely useless (an anti-pattern if you like to call it that way).