Javadoc
An Assignment MAY have a AssignTime setting. If the Object is an activity (Task,
Sub-Process, or Process), then the Assignment MUST have an AssignTime.
A value of Start means that the assignment SHALL occur at the start of the activity.
This can be used to assign the higher-level (global) Properties of the Process to the
(local) Properties of the activity as an input to the activity.
A value of End means that the assignment SHALL occur at the end of the activity.
This can be used to assign the (local) Properties of the activity to the higher-level
(global) Properties of the Process as an output to the activity.