14+ If In Sequence Diagram. A sequence diagram shows object interactions arranged in time sequence. If card inserted is valid.
They can be seen as oo if either diagram gets too cluttered with messages we can choose to model only the main flow of messages. You can show or hide sequence numbers of messages. Why is it hard to diagram this case as a sequence.
Here is a link where you can find some nice very simple , using alt fragment.
14+ If In Sequence Diagram. It shows the messages that pass between participants and objects in the system, and the order in which they occur. Sequence diagrams as part of uml play an important role within use case driven object oriented (oo) software engineering. The fragment executes only if the supplied condition is true. Equivalent to an alt only with one trace.