To place an existing model element on a diagram, you first locate the element in the browser and then drag it onto the diagram. However, you may be surprised at the result. Dragging the element can result in the element itself, an instance of the element, or a subtype of the element. You control which happens by holding the CONTROL-Key while dragging the element. In the dialog, you may choose to:
Paste the element as a Simple Link, meaning that the element itself will be pasted into the diagram (unless it is already on the diagram)
Paste the element as an Instance of the Element, meaning that you will create a new instance (object) of the element, separate from all other instances but with the same classifier (the element)
Paste the element as a New Child, meaning a new subtype of the element will be created.
Remember that when creating a new instance or a new subtype (child), the new element will be placed in the package that contains the diagram, not the package that contains the element.
If the element contains embedded elements (Exposed Interfaces, Parts, or Ports), the dialog box will include additional options. The advanced section lets you decide whether you want to show all of the embedded elements or to use the appearance of the element from another diagram (we call a template diagram). By (EA)<sup>2</sup> convention, we name the template diagram with the name of the element preceded by a '.' (single quotes not include). This makes the diagram easily found in the pop-up list of diagrams on which the element appears..
When dragging an Activity onto a diagram in the same manner as above, a slightly different dialog will appear. It allows you to select ‘as Invocation of Activity (Action)’, which means that you are creating an instance of the selected service the same way you created an instance in the description above.
