Tryton application platform - user role module

 Tryton is a high-level general purpose application platform. It is the base
 of a complete business solution as well as a comprehensive health and hospital
 information system (GNUHealth).
 .
 The user_role module allows to assign roles to user instead of groups.
 A *Role* is defined by a set of groups. When a role is added to a user, it
 overrides the existing groups. A role can be added to a user for a period.