Given the following quote for IfcWorkSchedules:
Nesting
The Object Nesting concept applies to this entity.
A work schedule can include other work schedules as sub-items through IfcRelNests relationship.
Aggregation
The Aggregation concept applies to this entity.
A work schedule can include other work schedules as sub-items. If not included in another work schedule it might be a part of a work plan (IfcWorkPlan) defined through IfcRelAggregates relationship.
The bolded sentence (emphasis mine) may be misinterpreted that aggregation is the concept used to put a workschedule as a sub-item of another work schedule. I believe this is not the intention. The intention is that Work Schedule → Work Schedule is nesting, and Work Plan → Work Schedule is aggregation.
I propose to remove the sentence in bold to remove this potential confusion.