Essentials of IBM Rational Requirements Composer, v3. Module 4: Creating a use-case model

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1 Essentials of IBM Rational Requirements Composer, v3 Module 4: Creating a use-case model Copyright IBM Corporation 2010, 2011

2 Module overview After completing this module, you should be able to: Explain the elements of use-case model Create a use-case specification Create a use-case diagram 2 Copyright IBM Corporation 2010, 2011

3 Define user and system requirements Business perspective User perspective System perspective Business Processes Use case model UI Sketch High-level business requirements Stakeholder needs Vision features UI specification Glossary Supplementary Spec Storyboard Business goals and objectives Business processes (as-is versus to-be) Features and use cases Stakeholder needs capture what Glossary the solution, will provide Business from a rules functional perspective. Features Functional requirements Non-functional requirements (including constraints) Use cases and user story elaborations Solution space User interface specification User interface Storyboard Problem space 3 Copyright IBM Corporation 2010, 2011

4 Actor An Actor represent roles that humans, hardware devices, or other systems can play in relation to the system under development. Actors are external to the system. A complete set of actors describes all the ways by which outside users communicate with the system. This illustration shows the Unified Modeling Language (UML) notation for an actor: Actor 4 Copyright IBM Corporation 2010, 2011

5 Use case Use case A use case is the specification of a set of actions performed by a system, which yields an observable result that is, typically, of value for one or more actors or other stakeholders of the system. (Unified Modeling Language -UML 2.0 ) Used to specify the behavior of a system, without revealing the internal structure of the system 5 Copyright IBM Corporation 2010, 2011

6 Use cases contain software requirements Each use case: Is a coherent unit of functionality provided by a system Describes sequences of actions that the system takes to deliver something of value to an actor Models a dialog between the system and actors Is a complete and meaningful flow of events from the perspective of a particular actor 6 Copyright IBM Corporation 2010, 2011

7 What is a use-case model? Describes the functional requirements of a system in terms of use cases Links stakeholder needs to software requirements Serves as a planning tool Consists of actors and use cases 7 Copyright IBM Corporation 2010, 2011

8 Capture a use-case model A use-case model is composed of: Use-case diagrams (visual representation) Use-case specifications (text representation) 8 Copyright IBM Corporation 2010, 2011

9 Use-case diagram Shows a set of use cases and actors and their relationships Defines clear boundaries of a system Identifies who or what interacts with the system Summarizes the behavior of the system Actor 1 Use-case diagram The system Use case 1 Use case 2 Use case 3 Actor 2 Actor 3 9 Copyright IBM Corporation 2010, 2011

10 Communicates-association Actor 1 Use Case A channel of communication between an actor and a use case. A line is used to represent a communicates-association. An arrowhead indicates who initiates each interaction. No arrowhead indicates either end can initiate each interaction. Actor 2 Actor 3 10 Copyright IBM Corporation 2010, 2011

11 Use-case specification A requirements document that contains the text of a use case, including: A description of the flow of events describing the interaction between actors and the system Other information, such as: Preconditions Postconditions Special requirements Key scenarios Subflows Use-case specification 11 Copyright IBM Corporation 2010, 2011

12 Use cases in Rational Requirements Composer Use cases exist as artifacts in the project. Use cases are elaborated with text in use-case specification artifacts. Use cases can be represented visually in use-case diagram artifacts. 12 Copyright IBM Corporation 2010, 2011

13 Creating a use-case specification Create a use-case specification as you would any other artifact. Select Use Case Specification in Artifact Type. 13 Copyright IBM Corporation 2010, 2011

14 Creating a use-case specification (continued) Add and edit use-case text in the Artifact editor. Edit attributes as necessary. 14 Copyright IBM Corporation 2010, 2011

15 Embedding artifacts You can embed artifacts or images in the use-case specification artifact. 15 Copyright IBM Corporation 2010, 2011

16 Artifact templates Artifact templates make it easier to create complete and consistent use-case specifications. 16 Copyright IBM Corporation 2010, 2011

17 Actors in Rational Requirements Composer Actors exist as artifacts in the project. 17 Copyright IBM Corporation 2010, 2011

18 Creating an actor artifact Create an actor artifact as you would any other artifact. Select Actor in Artifact Type. 18 Copyright IBM Corporation 2010, 2011

19 Creating an actor artifact (continued) Enter a text description for the Actor, and edit attributes as necessary. 19 Copyright IBM Corporation 2010, 2011

20 Creating a use-case diagram Create a use-case diagram as you would any other artifact. Select Use Case Diagram in Artifact Type. Then, build the diagram in the Use Case editor. Tool palette Actor Use case Association System boundary 20 Copyright IBM Corporation 2010, 2011

21 Lab 4: Working with use cases Complete these tasks: Open a use-case diagram. Open a use-case specification. Create a use-case diagram. 21 Copyright IBM Corporation 2010, 2011

22 Review What is the value of employing use cases? How do you represent use cases in Rational Requirements Composer? 22 Copyright IBM Corporation 2010, 2011

23 Module summary In this module, you learned how to: Create a use-case specification Create a use-case diagram 23 Copyright IBM Corporation 2010, 2011

24 24 Copyright IBM Corporation 2010, 2011