I used if-else condition in the sequence diagrams in a limited way. As long as the diagram is not getting complicated it is ok. If you have too many condition check. then think about splitting the diagrams.I have done that for authentication in my case.
Regarding your Q2, I completely omitted , 'what kind of component' information from my sequence diagrams, according to me, it is for explaining the message flow. In real life also we don't show component details in sequence diagrams.
Joined: May 22, 2011
Unni ,Thank you very much for your response..
Q1: I will use
Q2: I read in this forum, all the classes and public methods in a class diagram should use in sequnce diagram .
In class diagram i represented external web services as subsytem with steriotype <<webservices>>
that means i can use the same as a lifeline ..