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The example used in this part of the tutorial describes a simple information server. The information server provides certain data to users. The information server is the system under development. The name of the system instance is Server. An instance with name User represents a user that receives the data from the server.
The user starts interaction by sending message Init to the server. Then, the user requests data units by sending the message Request. Finally, the user terminates the interaction by sending the message Done. This behavior is specified by the MSC scenarios Request_Init, Request_Data and Request_Done. HMSC InfoServer provides the roadmap of the three scenarios.
MSC Request_Init describes the initialization of the information server. The User sends message Init to the Server and they both enter a data exchange loop (condition a_loop).
MSC Request_Data describes how the User sends message request to the Server and receives some data from Server (message Data). After this, both the Server and the User return to the data exchange loop (condition a_loop).
MSC Request_Done describes how the User sends message Done to the Server and breaks the connection between the User and the Server. The User terminates its involvement in the scenario (stop event at the end of the User instance at this MSC diagram). The Server continues its work.
HMSC InfoServer describes the roadmap for the three MSC scenarios.