On a sequence diagram, I can put a guard on an arrow to indicate conditional or iterative execution. But what if the condition or iteration step requires a sequence of actions between the user and the system? How do I show this in a sequence diagram?
For example, suppose the user enters data to a form, and the front
servlet checks it. If the data is invalid, the servlet forwards to the original
JSP with errors highlighted for correction,
and the user re-enters the data. This subsequence can happen repeatedly. If the data is good, the servlet processes the data and forwards to the next JSP. How do I show this on my sequence diagram?
Or should I just show the happy path, and add a note describing the extra steps that would have to be inserted in case the data is bad?