There are certain labels in our database that we have no term for, such as http://musicbrainz.org/label/62472b9a-778c-4559-bb43-0557f8542d2e . These labels are called "talent agencies," or simply "agencies." They provide services (such as artist management) that are currently irrelevant to MB, but in Japan in particular agencies retain a tremendous amount of creative control over artists. The following is a list of services talent agencies provide that we currently have ARs and situations for:
They often hold publishing rights, copyrights and phonographic copyrights to releases, recordings and works by artists under their umbrellas.
They release music under in-house imprints. In the case of physical releases, the manufacturing and distribution are handled by a major record company; digital releases are often handled directly (sometimes using a special imprint, sometimes not).
Executives from an agency are often credited as executive producers on releases.

There are a few other relationships I can think of that we may need ARs for in the future, but I will propose them in separate tickets.