This is a unique identifier linking a resource user type back to one specific resource owner, via a matching cermResOwnerId entry in cermResOwnerTable, that consumers of this type actually draw from. This linkage is what tells a management application which underlying physical resource, CPU versus memory for instance, a given class of process actually competes for, since a resource user type could in principle draw from more than one resource owner. If the IOS Process resource user type links to the resource owner ID for memory, a management tool knows that all processes classified under that type are being tracked specifically for their memory consumption.