CMMN — Expand TimeEventListener

For timeExpression, a string conforming to the ISO-8601 format is allowed.
While this format would allow time events occurring at a given point of time, it is impossible to specify time events that occur after a given period of time that starts with a state change of an instance.
For example, it would be impossible to specify that a time event occurs five days after an incoming invoice arrived.
Suggestion: TimerEventListener should contain another attribute that allows to specify a point of time when the duration given in timerExpression starts. This point of time should correspond to a state change of an instance.

Modify TimerEventListener Metamodel (Figure 6, section 5.4.2) to include references to PlanItem and CaseFileItem lifecycle state changes that triggers the start of a TimerEventListener