The Interested Parties Information Code (IPI) is an ISO standard similar to ISBNs for identifying the people or groups with some involvement with a particular musical work / compositions.
It is assigned by the Confédération Internationale des Sociétés d´Auteurs et Compositeurs.
In October 2001, the IPI database replaced the CAE database.
IPI numbers are attached to ISWC numbers, to allow !CISAC to attach information such as author, composer, and arranger to ISWC registered works. IPI numbers can also be used at the websites of other work registration organizations, such as BMI to locate works in their databases.
MusicBrainz doesn't currently store IPIs but could do so for label listings.