A very interesting article on metadata aggregation, Improving Metadata Quality: Augmentation and Recombination<, based on NSDL experiences has appeared.

Digital libraries have, in the main, adopted the traditional library notion of the metadata "record" as the basic unit of management and exchange. Although this simplifies the harvest and re-exposure of metadata, it limits the ability of metadata aggregators to improve the quality of metadata and to share specifics of those improvements with others. The National Science Digital Library (NSDL) is exploring options for augmenting harvested metadata and re-exposing the augmented metadata to downstream users with detailed information on how it was created and by whom. The key to this augmentation process involves changing the basic metadata unit from "record" to "statement." [Improving Metadata Quality: Augmentation and Recombination<]

It touches on our concerns at many points. I get no namecheck for use of recombinant :-)