A repository system may be tasked with producing an Inventory, but for which there are no stored studies that match the requested Scope. For instance, an organization may be producing an inventory of all nuclear medicine studies, and requests each of its several PACS and VNAs to create an Inventory with Modalities in Study = NM. A system that doesn't have any NM studies will create an empty Inventory object, which affirmatively declares that that system does not have any matching Studies as of the Content Date / Time.