Refactoring a class diagram

 

Study the following class diagram:

 

 

 

Here is a refactored version of that class diagram: 

 

 

 

 

 

These diagrams are a further illustration of the notation you've met for class diagrams. 

 

In the case of the first diagram, note that a nuclear laboratory inherits the characteristics of a laboratory and adds on its own additional features, whether properties or behaviours.  Similarly for nuclear equipment and equipment.  Clearly this means that the association (represented, as always, by the joining line) between laboratory and equipment is inherited by nuclear laboratory and nuclear equipment.   This is shown more clearly in the second diagram.  Diamond could have been inserted in the second diagram at the left end of each of the associations, as in the first diagram.

 

Note also that in the second diagram, we've created a parent class equipment from which both laboratory equipment and nuclear equipment are inheritors.