问题
Is it possible to describe an if-else structure in a system sequence diagram? If yes, how is this done?
回答1:
Here's more info about combined fragments from the VS 2010 sequence diagram documentation:
- UML Sequence Diagrams: Reference
- UML Sequence Diagrams: Guidelines
- Describing Control Flow with Fragments in UML Sequence Diagrams
回答2:
Yes, this can be done in UML 2 using the 'Alternative' combined fragment type, although personally I find them relatively difficult to read. There is a good example in this IBM DeveloperWorks article.
回答3:
Yes. This can be done in sequence diagrams. Not only if else,You can show loops, breaks and parallel etc.You have to learn combined fragment which is a sub-type of interaction fragment, to do that.
来源：https://stackoverflow.com/questions/2946650/how-to-show-if-else-condition-in-a-uml-system-sequence-diagram