What's the difference between “directory services” and “identity repositories”?

Question

I'm studying for the CCSP exam and the study material references two different terms which seems very similar:

Directory Services A system for managing identities and attributes. These allow the administrator to customize user roles, identities, and so on. Examples include: X.500 and LDAP, Microsoft Active Directory, Novell eDirectory, Metadata replication and synchronization.

Identity Repositories The directory services for the administration of user accounts and their associated attributes.

I'm confused. Does this mean that all Directory Services are also Identity Repositories? Or are there products/services that can be one but not the other?

If they are capable of being separate/distinct from one another, could someone perhaps provide a practical example?

Answer 1

The really simple version:

Directory services are the means to access structured data (including protocols) + a structured data repository.

The repository may contain all sorts of information, not necessarily just identity records. It may store quite a few things - think of it as a standard/means to publish and maintain a phonebook, yellow pages, and even an encyclopedia if you like. It has indexing, search, add/remove capabilities, etc.

The identity repository is a sub-set of a directory service, typically containing only identity-related information. So it's a limited subset of the directory service. May or may not include search, indexing, or other advanced directory capabilities, however it does typically require specific access mechanisms required for authentication and authorization.