ABSTRACT
This chapter focuses on requirements and analysis modeling. It introduces use case and collaboration diagrams. The chapter illustrates the requirements and analysis phases of communication protocol engineering by presenting the case of the session initiation protocol (SIP), RFC 3261. It divides into three subsections: SIP domain-specifics, the SIP requirements model, and the SIP analysis model. Use case diagrams are special kinds of graphs whose vertices are connected with arcs. Two types of vertices are found in use case diagrams, namely, actors and use cases. The actors represent humans, machines, or software components that are the users of the software under development. They are rendered as stick figures. Use cases represent possible uses of the software under development and are rendered as ellipses. An association between an actor and a use case has three categories of properties: general information about the association, table of constraints, and tagged values.
