A reference to a trajectoryStation in a wellbore.
The trajectoryStation may be defined within the context of another wellbore.
This value represents a foreign key from one element to another.
A pointer to the trajectoryStation within the parent trajectory.
This is a special case where we only use a uid for the pointer.
The natural identity of a station is its physical characteristics (e.g., md).
A pointer to the trajectory within the parent wellbore.
This trajectory contains the trajectoryStation.
A pointer to the wellbore that contains the trajectory.
This is not needed unless the trajectory is outside the
context of a common parent wellbore.