From NSDLWiki

aggregatorFor

The aggregatorFor relationship specifies the Agent that is logically responsible for selecting the contents of the Aggregator, and therefore "owns" the aggregation.

Types (Subject) that may contain this relationship 

Aggregator

Types (Object) that this relationship points to 

Agent

Predicate Namespace 

http://ns.nsdl.org/api/relationships#

Cardinality 

Exactly One aggregatorFor relationship is in a given Aggregator.

Usage and Semantics

This relationship indicates ownership and provenance only - it does not necessarily imply that the owning Agent actually introduced members into the Aggregation, or even has permission to do so directly. For example, Agents might act as proxies to another. A user might not log into and manipulate NCore objects directly - an application (with its own Agent) may to the actual work of building and populating aggregations on behalf of the user Agent. In that situation, the application Agent would have permission to modify the Aggregator membership, but that aggregation would be attributed to the user Agent through the aggregatorFor relationship.