Functional Modeling

Chapter 6

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Objectives■ Understand the rules and style guidelines

for activity diagrams.

■ Understand the rules and style guidelines for use cases and use case diagrams.

■ Understand the process used to create use cases and use case diagrams.

■ Be able to create functional models using activity diagrams, use cases, and use case diagrams.

Functional models

Used to document and understand requirementsDescribe business processes and interaction with environmentUsed for both as-is and to-be systemsTwo types: activity diagrams and use cases

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Functional models

Both activity diagrams and use cases are logical models – describe the activities of a system without specifying how the activities are implementedFocus on how business runs instead of implementation details

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Business Process Modeling with Activity Diagrams

Elements of an Activity DiagramGuidelines for Creating Activity Diagrams

Activity Diagrams

Used for any process modeling activity, esp. business process modelingProcess models show how a business system operates

Processes/activities performedHow objects/data move

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BPM With Activity Diagrams

A number of activities support a business process across several departmentsActivity diagrams model the behavior in a business process

Sophisticated data flow diagramsAddresses Parallel concurrent activities and complex processes

Activity Diagram syntax

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Activity Diagram syntax

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Activity Diagram Example

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Activity Diagram Example

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Creating Activity Diagrams1. Since an activity diagram can be used to model

any kind of process, you should set the context or scope of the activity being modeled. Once you have determined the scope, you should give the diagram an appropriate title.

2. You must identify the activities, control flows, and object flows that occur between the activities.

3. You should identify any decisions that are part of the process being modeled.

4. You should attempt to identify any prospects for parallelism in the process.

5. You should draw the activity diagram.

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USE-CASE DESCRIPTIONS

Use Cases

Formal way of representing how system interacts with its environmentIllustrates the activities that are performed by users of a systemProvide external or functional view of a process, not internal mechanism

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What are Use-Case Descriptions?

Describe basic functions of the system

What the user can doHow the system responds

Use cases are building blocks for continued design activities.

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How Are Use-Cases Created?

Two steps:Write text-based case descriptionsTranslate descriptions into diagrams

Describes one and only one function, but may have multiple paths.Developed working with users for content.

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Elements of a Use-Case Description

Use Case Name: ID: Importance Level:

Primary Actor: Use Case Type:

Stakeholders and Interests:

Brief Description:

Trigger:

Relationships: (Association, Include, Extend, Generalization)

Normal Flow of Events:

Subflows:

Alternate/Exceptional Flows:

Use Case Description Example

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Guidelines for Creating Use-Case Descriptions

Write each step in “SVDPI” formClarify initiator and receivers of actionWrite from independent observer perspectiveWrite at same level of abstractionEnsure a sensible set of stepsApply KISS principle liberallyWrite repeating instructions after the set of steps to be repeated.

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Your Turn

How would you make requirements gathering (interviews, questionnaires) more effective by knowing that eventually you will be creating use-case descriptions and diagrams?

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USE-CASE DIAGRAMS

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Syntax for Use-Case Diagram

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The Use-Case Diagram for Appointment System

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Use-Case Diagram with Specialized Actor

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Extend and Include Relationships

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CREATING USE-CASE DESCRIPTIONS AND USE-CASE DIAGRAMS

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Major Steps in Writing Use-Cases and Use-Case Diagrams

Identify the major use-casesExpand the major use-caseConfirm the major use-casesCreate the use-case diagram

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Identifying the Major Use-Cases

Review the activity diagramIdentify the system’s boundariesList the primary actorsList the goals of each primary actorIdentify and write the major use-casesCarefully review and revise use-cases

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Expand the Major Use-Cases

Choose one major use-case to expandFill in details on the use-case templateFill in the steps of the normal flow of eventsNormalize the size of each stepDescribe alternate or exceptional flowsSimplify and organize as necessary

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Confirm the Major Use Cases

Review the current setConsider semantics and syntaxHelpful to involve the users

Iterate the entire set of steps until all use cases are defined

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Create the Use-Case Diagram

Start with system boundaryPlace elements in order to be easy to readPlace actors on the diagramConclude by connecting actors to use cases by lines

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Writing Effective Use-Case Descriptions

Reading Task

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In pages 190 – 202 of the textbook, you will find an in-depth case study (CD Selections) of how to create use case descriptions and diagramsRead and understand the case study

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Summary

Use-case descriptions are the basis for further analysis and design.

Use-case diagrams present a graphical overview of the main functionality of a system.