I have done very similar things in code rather in SQL. just a bit of curious, I understood it is not possible many to many connections, but why don't you allow

I have done very similar things in code rather in SQL. just a bit of curious, I understood it is not possible many to many connections, but why don't you allow from cancel->started again? The business logic is always tend to be changed. I think this is a bad example using FSM here. IMHO, I will only want to apply stable, constant and (code)internal FSM to pgSQL. (Thought about a joke how to kill a programmer just needs change the requirements three times. lol) Good article anyway.