How to draw a Sequence Diagram for a Use Case that <<extend >> another Use Case?

Question

任何人都可以提供任何链接来显示如何绘制此类条件吗？

Answer 1

In addition to what Observer said, use a opt fragment AND a ref fragment inside.

• The opt fragment to set a piece of your sequence diagram as optional
• The ref fragment to delegate the content of the opt to another sequence diagram.

This way you have a 1-1 relationship between your use cases and your sequence diagrams, which is usually clearer.

See for example this picture : http://www.ibm.com/developerworks/rational/library/content/RationalEdge/feb04/3101_figure11.jpg

Answer 2

As you refer to a sequence diagram, you might be looking for the opt fragment: See an example . ( source )

That way you can conditionally include certain calls which are required by your extend use case.

You'll find the opt fragment explained in more detail on the web.