How to show an If else condition in a UML system sequence diagram

Question

Is it possible to describe the if-else structure in a system sequence diagram? If so, how is this done?

Answer 1

Here's more information about the merged snippets from the VS 2010 sequence diagram documentation:

• UML sequence diagrams: link
• UML Sequence Diagrams: Recommendations
• Description of control flow with fragments in UML sequence diagrams

Answer 2

Yes, you can do this in UML 2 using the "Alternative" combo fragment type , although I personally find them relatively difficult to read. This is an IBM developerWorks article .

Answer 3

Yes. This can be done in sequence diagrams. Not only otherwise, you can show loops, breaks and parallel, etc. You need to examine the combined fragment , which is a subtype of the interaction fragment, for this.