Relationship Between Users, Roles, and Login

Users, roles, and login have the following relationship:

A user typically belongs to one business unit, but can optionally belong to multiple business units. A user can have only one role in a business unit.
A user can optionally have different roles in different business units. For example, User A can have a catalog user role in the Finance business unit and a catalog administrator role in the IT business unit.
If the user does not specify a business unit at login, CA Service Catalog logs the user in to the default business unit defined for the user. The user is assigned the role defined for the user in that business unit.
If an integrating product (rather than CA Service Catalog) created the user, then the user is not assigned to a role or business unit. Instead, after the user logs in, the user receives the default role for all users. Examples of integrating products include CA Service Desk Manager, CA Business Service Insight, and Reservation Manager.