Use Case Modeling In UML
- 1. Use Case Modeling By Ramsha Ghaffr Syed Hassan Ali Hashmi Danial Raza
- 2. Outline Introduction What is Use Case Why We Use UseCase Reading Use Case Diagram Components Of Use Case Relationship Of Use Case How To Create Use case Diagram Benefits Of Use Case 2
- 4. What is UseCase • A formal way of representing how a business system interacts with its environment • Illustrates the activities that are performed by the users of the system • A scenario-based technique in the UML 4
- 5. A Use Case description will generally includes: ￮ General comments and notes describing the use case. ￮ Requirements ￮ Scenarios ￮ Constraints 5
- 6. Why We Use UseCase In a traditional Software Requirements Specification (SRS), features are presented without context. For example: The system shall log credit payments to the accounts receivable system. The lack of context makes room for ambiguity. ￮ When does this event happen? ￮ Is the order relative to other events significant? ￮ Who triggers the event? ￮ What happens when the accounts receivable system is unavailable? 6
- 7. Where to Use a Use Case Diagram? Use case diagrams specify the events of a system and their flows. But use case diagram never describes how they are implemented. Use case diagram can be imagined as a black box where only the input, output, and the function of the black box is known 7
- 8. Reading Use Case Diagram Starting with the actor check-in employee (1) you can find associations between the two use cases check-in (2) and express check-in (3). This means that persons who interact with the IT system as check-in employees can carry out the use cases check-in and express check-in. 8
- 10. Components/Elements A Use Case Modeling Contains ￮ Actors ￮ Use Case ￮ Communication Line ￮ System Boundaries 10
- 11. Actors A user or outside system that interacts with the system being designed in order to obtain some value from that interaction 11
- 12. Use Case A use case is a summary of scenarios for a single task or goal. 12
- 13. Communicaiton Line The relationships between and among the actors and the use cases. 13
- 14. System Boundaries A box that sets a system scope to use cases. All use cases outside the box would be considered outside the scope of that system 14
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- 17. RelationShips Use cases share different kinds of relationships. A relationship between two use cases is basically a dependency between the two use cases. Use case relationships can be one of the following: ￮ Association ￮ Include ￮ Extend ￮ Generalizations 17
- 18. Association Indicate that instances of one model element are connected to instances of another model element 18
- 19. Include Relationship ￮ When a use case is depicted as using the functionality of another use case in a diagram, this relationship between the use cases is named as an include relationship. ￮ Literally speaking, in an include relationship, a use case includes the functionality described in another use case as a part of its process 19
- 20. Include Relationship For example,: you can see that the functionality defined by the "Validate patient records" use case is contained within the "Make appointment" use case. Hence, whenever the "Make appointment" use case executes, the business steps defined in the "Validate patient records" use case are also executed. 20
- 21. Extend Relationship ￮ In an extend relationship between two use cases, the child use case adds to the existing functionality and characteristics of the parent use case. ￮ An extend relationship is depicted with a directed arrow having a dotted shaft, similar to the include relationship. ￮ The tip of the arrowhead points to the parent use case and the child use case is connected at the base of the arrow 21
- 22. Extend Relationship An extend relationship between the "Perform medical tests" (parent) and "Perform Pathological Tests" (child) use cases. The "Perform Pathological Tests" use case enhances the functionality of the "Perform medical tests" use case. Essentially, the "Perform Pathological Tests" use case is a specialized version of the generic "Perform medical tests" use case. 22
- 23. Generalization Relationship Generalization relationships are used in use-case diagrams to indicate that the child receives all of the attributes, operations, and relationships that are defined in the parent. 23
- 24. How To Create Use case Diagram 4
- 25. Creating Use Case ￮ List main system functions (use cases) in a column: – think of business events demanding system’s response – users’ goals/needs to be accomplished via the system – Create, Read, Update, Delete (CRUD) data tasks – Naming use cases – user’s needs usually can be translated in data tasks ￮ Draw ovals around the function labels ￮ Draw system boundary ￮ Draw actors and connect them with use cases (if more intuitive, this can be done as step 2) ￮ Specify include and extend relationships between use cases (yes, at the end - not before, as this may pull you into process thinking, which does not apply in UC diagramming). 25
- 27. Advantages ￮ Very simple to draw and understand which makes it good choice for analyst to use it during requirements gathering. ￮ A system can be viewed as whole with all of its use cases and actors/users how are initiating and having involvement in a particular use case. ￮ As there is no technicality involved in drawing or reading Use case diagram it benefits all stakeholder to understand the system. 27
- 28. Disadvantages ￮ They do not capture the non-functional requirements easily. ￮ There might be a learning curve for the developer and/or specially, the client in using these use cases. 28
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- 30. Summary ￮ Uses case describe example system behaviors (contracts) from the user’s point of view. ￮ Easy To Implement ￮ Easy To Read the systems ￮ 4 steps to create use cases. 30
- 31. Thank You 31