View Description:  This Diagram represents the progressive addition of contextual information as activities are involved in Studies or Experiments.  DefinedActivities have no context, just like a global library of things that can occur during the context of a study.  StudyActivities associate a DefinedActivity to a StudyProtocolVersion without assigning a relative time to it - just identifying that the activity will be used in the plan at some point.  PlannedActivities place the StudyActivity in the context of a relative timepoint in the course of a study or subject's participation in the study, forming a planned study calendar.  ScheduledActivities apply the PlannedActivities to a specific subject so the study calendar is now anchored to a real point in time.  PerformedActivities are ones that have occurred or at least begun and are done for a specific subject, site or study.<br/>