A role defines which applications and what parts of each application users can access and what those users or groups can do with the applications. For example, in a personnel application, all employees might be able to see phone numbers and email addresses, but only managers have access to salary information. This application would define at least two roles: employee and manager. Only users in the manager role are allowed to view salary information.
A role is different from a group in that a role defines a function in an application, while a group is a set of users who are related in some way. For example, the personnel application specify groups such as full-time, part-time, and on-leave. Users in these groups are all employees (the employee role). In addition, each user has its own designation that defines an additional level of employment.
Roles are defined in the deployment descriptor for the application. The application developer or deployer maps roles to one or more groups in the deployment descriptor for each application. When the application is being packaged and deployed, the application specifies mappings between users, groups, and roles, as illustrated in the following figure.