Is the IfcWorkSchedule project declaration mutually exclusive to aggregation within a relating IfcWorkPlan?

The IFC documentation describes two possible relationships on how an IfcWorkSchedule is related back to the IfcProject / IfcContext.

One scenario is that the IfcWorkSchedule is directly declared to the project.

Another scenario is that the IfcWorkSchedule is aggregated to an IfcWorkPlan, and the IfcWorkPlan is then declared to the project.

There are two potential interpretations:

  1. An IfcWorkSchedule is always declared to the IfcContext, and may be additionally included as an aggregate to zero or more IfcWorkPlans.
  2. An IfcWorkSchedule is declared to the IfcContext, unless it is included as an aggregate to one or more IfcWorkPlans

Can someone clarify?