ict117 week10 model validation s

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PowerPoint Presentation for Dennis, Wixom, & Tegarden Systems Analysis and Design with UML, 3rd EditionCopyright 2009 John Wiley & Sons, Inc. All rights reserved.

Moving on to DesignChapter 8: Dennis, Wixom and

Tegarden


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17/03/2011 ICT117 Systems Analysis & Design, Semester 2, 2010.

Includes John Wiley & Sons material.

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ObjectivesUnderstand the verification and validation of theanalysis models.Understand the transition from analysis to design.Understand the use of factoring, partitions, andlayers.Be able to create package diagrams.Be familiar with the custom, packaged, andoutsource design alternatives.Be able to create an alternative matrix.


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Key IdeasThe purpose of the analysis phase was tofigure out what the business needs. Thepurpose of the design phase is to figure outhow to provide it.The steps in both analysis and design phasesare highly interrelated and may requiremuch going back and forth i.e. iterative orspiral development


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VERIFYING AND VALIDATING

(V&V) THE ANALYSISMODELS


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WalkthroughsPeer reviews of models and diagrams thatwere created during analysisConducted by teams of analysts, designers, and

clientsMain purposes:

Test the fidelity of the models

Uncover errors or faults

Potential danger is that analysts may becriticised when the errors are uncovered !


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Functional Model V&VEvents in Use Case descriptions should map toactivities in the Activity DiagramObject node in an activity diagram must be mentioned

in Use Case descriptionsSequential ordering within the Use Cases shouldmatch the ordering in the Activity DiagramThere must be a one-to-one correspondence of UseCases in the Use Case Diagram and Use Casedescriptions.


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Functional Model V&VAll actors listed in a use case description mustbe portrayed on the use case diagramInclude stakeholders listed in the use casedescription as actors in the use casediagramAll relationships listed in a use casedescription must be portrayed on a usecase diagram


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Structural Model V&VEvery CRC card should be associated with aclass on the class diagramResponsibilities listed on the CRC card mustbe operations in a class on a class diagramCollaborators on the CRC card imply sometype of association on the class diagramAttributes listed on CRC cards must beattributes in a class on a class diagram


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Behavioural Model V&VActors and objects on sequence diagrams must beincluded on communication diagramsMessages on sequence diagrams require associations

on communications diagramsEvery message on a sequence diagram must appearas a message on an association in thecorresponding communication diagramGuard condition messages in sequence diagramsrequire equivalent guard conditions on thecorresponding communication diagrams


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Structural Model V&VThe sequence number on message labels incommunications diagrams must correspond to thetop-down ordering of the messages being sent onthe sequence diagramState machine transitions must be associated with amessages on sequence and communicationdiagramsAll entries in a CRUD matrix imply a message beingsent between an actor or object and another


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EVOLVING THE ANALYSIS

MODELS INTO DESIGN MODELS


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FactoringCreating modules that account for similaritiesand differences between units of interestNew classes

GeneralisationAggregation

AbstractingRefinement


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LayersConsider system environment information tohelp evolve the analysis modelModel-view-controller (MVC) architectureSeparating application logic from userinterface logic


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5 LayersFoundationProblem DomainData ManagementHuman-Computer InteractionPhysical Architecture


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PACKAGES AND PACKAGE

DIAGRAMS


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PackageA general construct that groups units togetherUsed to reduce complexity of modelsA package diagram shows packages only


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Package Diagram for 5 Layers


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Building Package DiagramsSet the contextCluster classes together based on sharedrelationshipsModel clustered classes as a packageIdentify dependency relationships amongpackagesPlace dependency relationships betweenpackages


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DESIGN STRATEGIES


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Custom DevelopmentAllows for meeting highly specialisedrequirementsAllows flexibility and creativity in solving

problemsEasier to change componentsBuilds personnel skillsMay tax firms resourcesMay add significant risk


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Packaged SoftwareSoftware is already writtenMay be more efficientMay be more thoroughly tested and provenMay range from components to tools to wholeenterprise systemsBut clients must accept the functionality providedMay require changes in how the firm does

businessMay require significant customization orworkarounds to support mandatory processes


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System IntegrationThe process of combining packages, legacysystems, and new softwareKey challenge is integrating dataWrite data in the same formatRevise existing data formatsDevelop object wrappers


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OutsourcingHire an external firm to create the systemThey may have more skillsThey may extend existing company resourcesCaveats:Never outsource what you dont understandCarefully choose the vendorPrepare contract and payment style carefully


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Selecting a Design StrategyBusiness needIn-house experienceProject skillsProject managementTime frame


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Selecting a Design StrategyUse CustomDevelopment when Use a PackagedSystem when Use Outsourcingwhen

Business Need The business need isunique

The business need is

common

The business need is

not core to the

business

In-house Experience In-house functionaland technical

experience exists

In-house functional

experience exists

In-house functional

or technical

experience does not

exist

Project Skills There is a desire tobuild in-house skills

The skills are not

strategic

The decision to

outsource is a

strategic decision

Project Management The project has ahighly skilled project

manager and a

proven methodology

The project has a

project manager who

can coordinate

vendors efforts

The project has a

highly skilled project

manager at the level

of the organization

that matches the

scope of the

outsourcing deal

Time frame The time frame isflexible

The time frame is

short

The time frame is

short or flexible


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DEVELOPING THE ACTUAL

DESIGN


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The Alternative MatrixCombines several feasibility analyses into onegridRevisits technical, economic, and

organisational feasibility


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SummaryVerifying and Validating the Analysis ModelsEvolving the Analysis Models into DesignModelsPackages and Package DiagramsDesign StrategiesDeveloping the Actual Design

ict117 week10 model validation s

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