software engineering paradigms

8/3/2019 Software Engineering Paradigms

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Software Engineering

Paradigms

What happens in the life of software


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Software Engineering

Layers

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a quality focus

process model

methods

tools


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The Primary Goal:

High Quality

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Remember:

High quality = project timeliness

Why?

Less rework!


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Classic Life Cycle\Waterfall Model

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SystemEngineering

Analysis

Design

Code

Testing

Maintenance


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Waterfall Model

CharacteristicsThe classic life cycle - oldest and most widelyused paradigm

Activities flow from one phase to anotherIf there are corrections, return to a previousphase and flow from there again

Major advantages: Good for planning and well-defined/repeated projects

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Problems of Waterfall

ModelReal projects often follow the sequenceAll requirements may not be stated

explicitly by customerCustomer only sees the results aftersome time

Developers are often delayed atcertain phases

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Prototyping Model

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Stop

Requirementsgathering and

refinement

Buildingprototype

Quickdesign

Customerevaluation

Refiningprototype

Engineerproduct

Start

listento

customer

build/revisemock-up

customertest-drivesmock-up


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Prototyping Model

CharacteristicsDeveloper and customer determineobjectives and draft requirements

Prototype quickly produced and

evaluated by customer

Prototype then refined, and re-evaluated

Process iterated, before final productdevelopment

Advantages: Customer participation andbetter requirements

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Problems of Prototyping

ModelProblem 1: Customer may seeprototype as working model andexpects fast results

Problem 2: Developer compromisedwhen producing prototype quickly, e.g.different operating system or

programming language

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Six Task Region

Spiral Model

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Customer Communication-tasksrequired to establish effectivecommunication between developer andcustomer.

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Planning-tasks required to defineresources, timelines, and other projectrelated information.

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Risk analysis-tasks required to assessboth technical and management risks

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Engineering-Tasks required to build oneor more representations of the application

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Construction & Release-Tasksrequired to construct, test, install andprovide user support (e.g., documentationand training)

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Customer Evaluation-Tasks required toobtain customer feedback based onevaluation of the software representationscreated during the engineering stage and

implementation during the installation stage 17


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Spiral Model

CharacteristicsOriginally proposed by Boehm, couplesiterative nature of prototyping and thesystematic aspects of waterfall model

Software is developed in series ofincremental releases

Each iteration produces a more complete

productBetter management through risk analysis

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Problems of Spiral Model

May be difficult to convince customersthat evolution is controllable

Demands risk assessment expertise -major risk will cause problems if notidentified

Relatively new and not widely used -cannot determine performance

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Fourth GenerationTechniques (4GT)

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4GT Characteristics

Use of software tools that allowsoftware engineer to specify s/wcharacteristics at higher level

The tools generate codes based onspecification

More time in design and testing -

increase productivity

Tools may not be easy to use, codesgenerated may not be efficient

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Conclusion

The paradigm used for development ofsoftware depends on a number of factors

People - staff & users

Software productTools available

Environment

Existing models makes development processclearer, but they can be evolved to becomenew paradigms

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References

Software Engineering: A PractitionersApproach 5th Ed. by Roger S.Pressman, Mc-Graw-Hill, 2001

Software Engineering by IanSommerville, Addison-Wesley, 2001

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software engineering paradigms

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