In the example depicted in Figure 1 students are enrolling in courses with the potential help of registrars. Figure 3 depicts how Figure 1 could be reorganized with packages. I use packages only when my diagrams become unwieldy, which generally implies they cannot be printed on a single page, to organize a large diagram into smaller ones. Packages are depicted as file folders and can be used on any of the UML diagrams, including both use case diagrams and class diagrams. Packages are UML constructs that enable you to organize model elements (such as use cases) into groups. System boundary boxes are rarely used, although on occasion I have used them to identify which use cases will be delivered in each major release of a system. Anything within the box represents functionality that is in scope and anything outside the box is not. You can draw a rectangle around the use cases, called the system boundary box, to indicates the scope of your system. The arrowheads are typically confused with data flow and as a result I avoid their use. The arrowhead is often used to indicating the direction of the initial invocation of the relationship or to indicate the primary actor within the use case. Associations are modeled as lines connecting use cases and actors to one another, with an optional arrowhead on one end of the line. An association exists whenever an actor is involved with an interaction described by a use case. Associations between actors and use cases are indicated in use case diagrams by solid lines. An actor is a person, organization, or external system that plays a role in one or more interactions with your system. A use case describes a sequence of actions that provide something of measurable value to an actor and is drawn as a horizontal ellipse. Figure 1 provides an example of a UML 2 use case diagram.Use case diagrams depict: They are useful for presentations to management and/or stakeholders, but for actual development you will find that use cases provide significantly more value because they describe “the meat” of the actual requirements. UML 2 use case diagrams overview the usage requirements for a system.

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