The Use-Case Model

Last updated: May 10, 2006

Objectives: After completing this module, you'll be able to

• Describe a use-case model, its components, and its importance.

• Explain what is used to create use-case diagrams in Rose.

• Use the Rose tool to create a use-case diagram to clearly illustrate what the system will do.

• Use the Rose tool to create an activity diagram to visually illustrate a use case's flow of events.

The Use-Case Model:

• Is created in the Use-Case View of Rose.

• Is a model of the system's intended functions and its environment.

• Serves as a contract between customer and developer.

• Is essential to analysis and design and test activities.

• Can include use-case diagrams, use-case flow of events, supplemental information, and activity diagrams.

• Is created using artifacts developed by the software architect and system analysts in concert with the customer. An artifact is information produced, modified, or used by a process. It defines and area of responsibility and is subject to version control. An artifact can be a model, a model element, or documentation.

Use-Case Diagrams

• Can be modeled in a number of ways:

  • All actors and use cases (global view).

  • All the use cases for a selected actor.

  • A single use case and all its relationships.

  • All the uses cases used in an iteration.

  

  　

• Are typically created from numerous sources that may include the following:

  • Glossary

  • Stakeholders request

  • Vision document

  • Use-case modeling guidelines

  • Business use-case model

  • Business object model

  • Supplemental specifications

• Relationships:

  • The navigation direction represents who is initiating the communication.

  • The end with the arrow indicates who or what is receiving the communication.

Flow of Events:

• In Rose, you include each use case's flow of events in the Use-Case View.

• A flow of events is included under its use-case package in Rose and can be accessed directly from Rose once it's attached.

Artifacts:

• Can be both input and output artifacts depending on the activity.

• Are important to the use-case model and should be attached to the model in Rose. These documents may include the glossary, vision, stakeholder requests, business use-case model, and so on.

• Can be accessed directly from Rose once they're attached.

Activity Diagrams:

• Activity diagrams can also be used in business modeling and to model the workings of an operation, an object, or anything that involves modeling the sequential steps in a computational process.

• Activity diagrams represent the dynamics of the system.

• Activity diagrams are not required. Some prefer its textual counterpart, the flow of events. It's up to you whether you create them to illustrate the workflow of a use case.

• Transitions can be labeled with events, guard conditions, or actions using the transition's Specification window in Rose.

• Swimlanes:

  • Each swimlane should represent a responsibility for part of the overall workflow, carried by a part of the organization. A swimlane may eventually be implemented by an organization unit or a set of classes in the business object model.

  • The relative ordering of swimlanes has no semantic significance. Each activity is assigned to one swimlane and transitions may cross lanes.

  

Reports:

• Show Usage: The Show Usage report lists all the locations where the selected item is used as a supplier in a relationship.

• Many items can be suppliers in relationships.

  • Classes, actors, and use cases can be suppliers for associations.

  • An operation can be a supplier for a message.

  • Activities, synchronizations, and states can be suppliers for state transitions.

  • This report can be used with all Rose diagrams, including use-case and activities diagrams.

Create a Use-Case Diagram:

• Add the Use-Case Diagrams to the Browser:

  • Open Lab4_1.mdl

  • Expand Use Case View －＞ Expand Use-Case Model

    • look at the actors under Actors

    • look at the use cases under Use Cases

  • Create Realtor View for actor Realtor

  • Create Maintain Personal Planner View for use case Maintain Personal Planner.

  

  　

• Add the Actors and Use Cases to Diagram:

  • Double-click Realtor View

  • Referencing the Global View of Actors and Use Cases, determine the use cases associated with the Realtor actor.

  • Drag the Realtor actor and its use cases from the browser into the diagram window.

    • Notice that the association relationships are also added automatically.

  • Similarly, add the actors and use cases for Maintain Personal Planner View.

  

  　

• Add Use-Case Flow of Events:

  • Right-click Apply for Loan －＞ Select a New File

  • Select ApplyForLoan.txt

    • You can now double-click the file to open it from Rose.

  • Similarly, add MaintainPersonal Planner.txt for Maintain Personal Planner; add SearchForHome.txt for Search For A Home.

  

  　

• Add Project Artifact:

  • Add the Home Realty System's Problem Statement (ProblemStatement.txt) to the Use-Case Model.

• Add text to the documentation window to describe one of your use-case diagrams.

• Change the line and/or fill color of a use case.

Create an Activity Diagram:

• Add Activity Diagram to the Browser

  • Right-click Maintain Personal Planner use case (NOT the package) －＞ New －＞ Activity Diagram

  • Name the diagram: Basic Flow －＞ click outside the name box

  • Open Basic Flow

• Add Activities, start and End States, Transitions, Decisions, and Guard Conditions

  • Referencing the following Activity Diagram, add the activities to the diagram.

  

  • Add the start state and end state(s) to the diagram.

  • Add the transitions, decisions, and guard conditions

    • For decisions: Add the decision icon －＞ Add the transitions

    • For guard condition text: Open the trasition's Specification Window －＞ｄ

    • To check your competed use-case model : Open Lab4_2.mdl

• Run the Show Usage report on any element in a use-case or activity diagram:

  • Open the diagram －＞ Select a model element －＞ Report －＞ Show Usage