In a proper case tool, even though the diagrams are used to create and display the elements in the model, the model element information is not stored in the diagrams, but in a model file, or repository. Model elements can appear on more than one diagram. When the properties of an element are changed in one diagram, the changes are reflected in all other diagrams that use it. This would be difficult if each diagram had it's own copy of a model element. The only information contained within the diagram is:
