The ISNI was developed in 2010 and published by ISO in 2012. While we have identifiers for just about every form of intellectual property, the ISNI identifies the people and organizations that create that intellectual property. Authors, composers, musicians, actors, directors, producers, public figures, music labels, publishing companies – anybody who has created or contributed to the creation of intellectual property is eligible for an ISNI.
ISNI is particularly helpful in two cases – differentiating people with the same or similar names, and collocating people who have made multiple contributions across a variety of media. Large publishing houses, for example, frequently have similarly-named authors in their stables and royalty tracking can be made easier with an identifier like ISNI.
In addition to helping with rights tracking, the ISNI plays a central role in connecting various different sorts of systems together. In use by Wikipedia, Musicbrainz, the British Library, Harvard University, and a number of other organizations, ISNI provides a bridge between all these data sets, a way of linking all these different collections together with a common identifier. This enhances discoverability across the web.
ISNI registration agencies tend to form around specific interests.
The BnF, for example, is focused on French-related interests. Ringgold registers only organization names. The British Library is focused on UK-related contributors. Iconoclaste specializes in French-Canadian musicians. Numerical Gurus is focused on creators of books, music, video and film, and other media and entertainment content.
Numerical Gurus is the only registration agency in the US, and it is the only registration agency that also provides applications for individual contributors. The rest only do bulk uploads.
More information about ISNI can be found here.