Recommender Service
Types of Relationships  metadataProviderFor... Example .org 10006 M 10005 Aggr 2004 MDP  3004 NSDL RS Agent  1004 NSDL Recom-mended 1005 M 4005 Aggr 2005 NSDL Collections 1002 M 4002 Aggr 2002 MDP  3000 NSDL Agent 1000 NSDL BigBang