What is Union?
Union is the ability to create a global list where each user is represented once and only once, even if they have multiple accounts spread across the identity infrastructure of an enterprise organization. Union requires some kind of criteria, one or more attributes, to detect and correlate same-users across systems. This is the common, global identifier. A match based on this attributes(s) allows us to remove duplicates. The result is a “union compatible” operation, where all users are represented exactly once, and only once, in the virtualized global list. The value of the union operation is key for any solid identity service.
Why is Union an essential function for an identity service?
User overlap can occur for a number of different reasons. There could be one user listed numerous times, or multiple users with the same name spread across disparate data silos. To create a global list without duplicate identities, you need to correlate and disambiguate the identities. The result of a union is a unique list of users that is indexed for each system which enables fast and easy lookups. The reason this capability is critical for an identity service is because it makes the identification of a user more accurate and efficient.