I'm drawing a flow diagram which should visualize the communication between 4 services I created.Now I've got a question I'm not quite sure about. There are two ways the services could be started. Is it allowed to have multiple starting-points in a flow chart?And: do I have to visualize error handling, like a service not being available? I think this doesn't belong in a flow chart, perhaps?
Can a flow diagram have more than one start?
design;flowchart;chart
If you are using flowcharts, then you can have 3 separate flowcharts. 1 to represent the overall view showing the decision that leads to initiating the service in the 2 different ways you say you have in your case. The other two diagrams will detail the process in each scenario. Flow charting is a loose technique with hardly any rules beyond what the shapes mean. This causes an inconsistency problem sometimes.For documenting OO systems, I suggest you use UML 2.0+ and in particular Activity diagrams (similar to flow charts) and Sequence diagrams as well as use cases. 