An information system consists of a number of services. We distinguish user facing services and non-user facing services. User facing services (e.g. register a client, sanitize case files, login) can be made available for a limited number of roles, giving each user access to precisely the services he or she is meant to see. In the diagram, user-facing services are colored corresponding to the roles they serve. Non-user facing services are not colored. Therefore, they are used exclusively by other software. Services can be either stateful or stateless. In the diagram, stateful services are drawn with a data container inside.