Elements of Sequence Diagrams

 

1.   Use case text runs down the left-hand side of the diagram.  Break up the text with white space so it’s easy to follow.

2.   Objects from the robustness diagram are listed across the top of the diagram. A dotted line runs from that box down the length of the page.

3.   Messages are represented as arrows between objects.

4.   Methods (operations) are shown as rectangles that lie on top of the dotted lines that belong to the objects to which you’re assigning the methods.