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.