Requirements are specified as a list of goals and non-goals for the project. A link to the UML home page is provided below. UML diagrams are analysis and design tools, and each diagram format can support multiple levels of abstraction. In this document a balance has been struck between using a standard diagram format for requirements elaboration, and maintaining a high level of abstraction. These can be human beings or software systems.
Ellipses represent use cases, i.e. actions or units of functionality in a system.
Lines between actors and use cases indicate a participation of the actor in the use case. A scenario is a group of logically connected use cases. The document uses UML sequence diagrams to illustrate detailed use case scenarios. Arrows with a solid head represent a message sent from one actor to another. The arrow points from sender to receiver.