Question

Here’s a very quick example for my problem:

http://img19.imageshack.us/img19/3575/workertool.png

(I’m not allowed to post the image here because I’m a new user)

The source code for both classes looks like this:

public abstract class Worker{

  private Tool myTool;

}

public class ABCWorker extends Worker{

  public ABCWorker(){
    myTool = new ABCTool();
  }

  public work(){
    tool = (ABCTool) myTool;
    //use tool to do some work
  }

}

How do I correctly model this in UML? In my opinion, there are only three possibilities:

1) The way I did it in the example. This is wrong, however, because it says that an ABCWorker can use any tool. However, it can only use an ABCTool.

2) Put a second association between ABCWorker and ABCTool. Obviously wrong because it would mean an ABCWorker uses two tools, an ABCTool and a generic one.

3) Only put one association between ABCWorker and ABCTool. Also wrong, because it omits the relationship between Worker and Tool.

So how should I do it?

Answer 1

Some things just cant be shown on a class diagram.
This for example, is one of those cases, where you cant really show the interaction between objects. And that is normal, because this is a class diagram.

If this is really important to you, then you should model it using a more appropriate diagram, in order to explain this.