The general EPC conventions (sequence in connection flow Event - Function - Event) result in the following guidelines for creating the graph for a process instance:
A process instance must begin and end with one or more events and contain at least one function.
As rules, process instances can contain exclusively AND rules, as they represent actual working processes.
An event may not be followed by a branching rule (OR or XOR).
A function may be followed by another function. The linking event between two functions may be removed.
An event may only be followed by a function or a joining rule.