Registries are a programmatic interface for master data. They can operate as a layer above existing internal databases (which are otherwise not reachable to the ecosystem). Registries enable other ecosystem players and developers (public, private, and non-profit) to access data via Open APIs, and build a variety of market solutions (eg. rating applications or locator applications in different languages) to share information in the Registry for end users.
The API documentation for third party developers to read and search the Registry data is available at this link.