Names of abstract classes, such as Payment, are in italics. UML class notation is a rectangle divided into three parts: class name, attributes, and operations. Class diagrams are static - they display what interacts but not what happens when they do interact. The extension point, which determines when the extended case is appropriate, is written inside the base case.ġ0 Class Diagram A Class diagram gives an overview of a system by showing its classes and the relationships among them. Extend notation is a dotted line, labeled >, and with an arrow toward the base case. An extend relationship indicates that one use case is a variation of another. In the diagram, include notation is a dotted line beginning at base use case ending with an arrows pointing to the include use case. Both Make Appointment and Request Medication include Check Patient Record as a subtask. Includes are especially helpful when the same use case can be factored out of two different use cases. Include relationships factor use cases into additional ones. Generalization appears as a line with a triangular arrow head toward the parent use case. A child can be substituted for its parent whenever necessary. Pay Bill is a parent use case and Bill Insurance is the child. A use case generalization shows that one use case is simply a special kind of another. A system boundary rectangle separates the clinic system from the external actors. The following use case diagram expands the original medical clinic diagram with additional features. system boundaries generalizations includes extensions This section covers the following UML™ use case features. A simple use case diagram can be expanded with additional features to display more information. Every use case diagram has actors, use cases, and communications. Use case diagrams give an outsider's view of a system. The connection between actor and use case is a communication association (or communication for short). The picture below is a Make Appointment use case for the medical clinic. Actors are simply roles that people or objects play. An actor is who or what initiates the events involved in that task. A use case is a summary of scenarios for a single task or goal. Communications are lines that link actors to use cases. The receptionist finds the nearest empty time slot in the appointment book and schedules the appointment for that time slot. Here is a scenario for a medical clinic.ħ Use Case Scenario "A patient calls the clinic to make an appointment for a yearly checkup. A scenario is an example of what happens when someone interacts with the system. Use case diagrams are closely connected to scenarios. The emphasis is on what a system does rather than how. The collection of scenarios for a use case may suggest a suite of test cases for those scenarios.Ħ Use case Diagram Use case diagrams describe what a system does from the standpoint of an external observer. Their notational simplicity makes use case diagrams a good way for developers to communicate with clients. New use cases often generate new requirements as the system is analyzed and the design takes shape. Sequence diagrams Collaboration diagrams State chart diagrams Activity diagrams Component diagrams Deployment diagramsĥ Use case Diagram Use case diagrams are helpful in three areas.ĭetermining features (requirements). Several modeling tools are wrapped under the heading of the UML™, which stands for Unified Modeling Language™.ģ Why is UML important? Describe OO architecture of the Systemĭescribe system behavior Describe system interaction with user or other systems Describe System activities Describe System components Describe System states Describe System operabilityĤ UML Diagrams Use case diagrams Class diagrams Object diagrams The model abstracts the essential details of the underlying problem from its usually complicated real world. 1 Introduction to Unified Modeling Language (UML)Ģ Introduction The heart of object-oriented problem solving is the construction of a model.
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