0639 Causal relationship between activities

Many models of drilling activities tag each activity with 'what' and 'why' codes. In Epicentre, all 'what' information is recorded through the activity_type. This includes the recording of significant observations such as a kick, which is modeled as an event activity. However, there is no direct equivalent to the 'why' code. The semantics of the 'why' code is to indicate that the purpose of the activity is to recover from a particular event. So it represents a causal dependence of an activity on an event. The fact that one activity follows another can be modeled in Epicentre using the schedule_constraint. However, the semantics of this usage are unclear. There is a need in Epicentre for a construct that clearly models causal dependence between activities. Note that this causal dependence includes some repesentation of the 'state' of an operation.

Consolidated changes: (0562, 0803)

Add cause and effect to the activity model.

The entity activity_cause_and_effect was added. This is a subtype of association and has two relationships to activity - one pointing to the causing activity and the other to the resulting activity.

Added objects:
activity_cause_and_effect (Entity)
activity.caused (Attribute)
activity.result_of (Attribute)

Modify diagram

Add the new entity to diagram AC2.

Modified objects:
AC2:_Activity_Effects (Diagram)