Class diagram questions - Model and copies, Class reuse


even though I am already in the software business for a long time I am fairly new to UML. I decided to use Visual Paradigm and started my first project using this tool and now run into some issues that I would like to address here. I am only working on the class diagram right now.

  1. Model and copy classes
    When I create a new class and copy it, then the original box is indicated with a “M” in the upper left corner. The new box is indicated with an “a”.

1.1. “M” stands for Model right ?
1.2. What does “a” stand for ?
1.3. Is there any difference in tool functionality between the both ?
1.4. If I delete the “M” box and only “a” boxes are left, is this an issue?
1.5. How can I restore a missing “M” box?

  1. Class reuse
    I work alot with interfaces and most of the time interfaces use other interfaces or even derive from them.

To make things simpler the following interfaces and classes are used.
Interfaces: Ia, Ib, Ic, Id whereas Ia uses Ib, Ic, Id
Classes: Ca, Cb

In all the interfaces make up for four boxes. The two classes Ca, Cb inherit from interface Ia.

Now the problem is that these two classes Ca, Cb are not really close to each other on the diagram I am creating. There are good reasons for that. Nevertheless I do not like to make now connections from one end of the diagram to the other to make sure that both classes Ca and Cb are connected to the interface Ia.

Therefore what I do is that I copy the Ia, Ib, Ic, Id structure and bring the copy and the original close to either class and then connect. Therefore the interface boxes are doubled. Is this a bad approach? I fear that maintenance gets really messy with time. Any recommondations?