Exactly one role on the customer side as well as exactly one role on the provider side is participating in every interaction. Such roles are grouped to reach a higher abstraction level. A role can be mapped to organizational units and is associated with certain rights, which contributes to the area of security management. In this paper we are concentrating on the usage phase at an abstraction level which allows to model a service generically.
As stated in the previous subsection, there are two major interaction classes: usage and management interactions. According to this, we identified two main roles on the customer side: Users, who actually use the service and a customer, who is interested in maintaining a subscribed service and therefore performs all the management activities on the customer side. On the provider side all necessary activities for enabling service usage as well as service management have to be performed. Since these activities cannot be strictly separated on the provider side's internal processes we only introduce the role provider for the provider side at this stage which is sufficient for the scope of our service model presented in the following section. Of course a more detailed analysis leading to more than three roles is possible.
Even though our methodology is more powerful in respect of application in any stage of the service life cycle and the roles involved, for the remainder of the paper, we use the roles user, customer and provider to describe the relevant interfaces, relations and objects in our service model during the usage phase.