mba 3rd spiral model

8/2/2019 Mba 3rd Spiral Model

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General Idea of IterativeGeneral Idea of IterativeModelsModels-- Spiral ModelSpiral Model


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Waterfall ModelWaterfall Model RevisitedRevisited

Disadvantages ofWaterfall Model

1. Real projects are rarely so straightforward and sequential

2. It is generally not possible to completely define (and

freeze) all the requirements at the start of the project

3. Problem is discovered in testing?

4. Over-Budget


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Iterative ModelsIterative Models

Whats an Iteration?

Whats an Iteration?

Iterative Design: Code as much as you can questions surface, then start

over.

Every model well talk about below is a variation on the Iterative Model.


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Spiral ModelSpiral Model

Strength and WeaknessesStrength and Weaknesses Strengths

Introduces risk management

Prototyping controls costs

Evolutionary development Release builds for beta testing

Marketing advantage

Weaknesses

Lack of risk management experience Lack of milestones

Management is dubious of spiral process

Change in Management

Prototype Vs Production


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spiral model (spiral lifecyclespiral model (spiral lifecycle

model)model)

The spiral model, also known as the spiral

lifecycle model, is a systems developmentlifecycle (SDLC) model used in information

technology (IT). This model of development

combines the features of the prototyping model

and the waterfall model. The spiral model isfavored for large, expensive, and complicated

projects.


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ApplicationsApplications

For a typical shrink-wrap application, the spiral

model might mean that you have a rough-cut of

user elements (without the polished / pretty

graphics) as an operable application, add featuresin phases, and, at some point, add the final

graphics.

The Spiral model is used most often in large

projects and needs constant review to stay on

target. For smaller projects, the concept ofagile

software development is becoming a viable

alternative.


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AdvantagesAdvantages

Estimates (i.e. budget, schedule, etc.) get more

realistic as work progresses, because important

issues are discovered earlier.

It is more able to cope with the (nearly

inevitable) changes that software development

generally entails.

Software engineers (who can get restless with

protracted design processes) can get their

hands in and start working on a project earlier.


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Spiral ModelSpiral Model

Determine

objectives,alternatives,

constraints

Evaluate

alternatives,identify and

resolve risks

Develop verify

next level

product

Plan next

phases


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Spiral Model DescriptionSpiral Model Description

The development spiral consists of four quadrants as shown inthe figure above

Quadrant 1: Determine objectives, alternatives, and constraints.

Quadrant 2: Evaluate alternatives, identify, resolve risks. Quadrant 3: Develop, verify, next-level product.

Quadrant 4: Plan next phases

Although the spiral, as depicted, is oriented toward softwaredevelopment, the concept is equally applicable to systems,

hardware, and training, for example. To better understand the

scope of each spiral development quadrant, lets briefly address

each one.


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Quadrant 1: Determine Objectives,Quadrant 1: Determine Objectives,

Alternatives, and ConstraintsAlternatives, and Constraints

Activities performed in this quadrant include:

Establish an understanding of the system or product

objectivesnamely performance, functionality, and ability to

accommodate change.

Investigate implementation alternativesnamely design,

reuse, procure, and procure/ modify

Investigate constraints imposed on the alternativesnamely

technology, cost, schedule, support, and risk. Once the

system or products objectives, alternatives, and constraints

are understood, Quadrant 2 (Evaluate alternatives, identify,

and resolve risks) is performed.


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Quadrant 2: Evaluate Alternatives, Identify,Quadrant 2: Evaluate Alternatives, Identify,

Resolve RisksResolve Risks

Engineering activities performed in this quadrant select analternative approach that best satisfies technical,

technology, cost, schedule, support, and risk constraints.

The focus here is on risk mitigation. Each alternative is

investigated and prototyped to reduce the risk associated

with the development decisions. Boehm describes theseactivities as follows:

This may involve prototyping, simulation, benchmarking,

reference checking, administering user questionnaires, analytic modeling, or combinations of these

and other risk resolution techniques.


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Quadrant 3: Develop, Verify, NextQuadrant 3: Develop, Verify, Next--LevelLevel

ProductProduct

If a determination is made that the previous

prototyping efforts have resolved the

COIs/CTIs, activities to develop, verify, next-level product are performed. As a result, the

basic waterfall approach may be employed

meaning concept of operations, design,

development, integration, and test of the nextsystem or product iteration. If appropriate,

incremental development approaches may

also be applicable.


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Quadrant 4: Plan Next PhasesQuadrant 4: Plan Next Phases

The spiral development model has one characteristic

that is common to all modelsthe need for advanced

technical planning and multidisciplinary reviews atcritical staging or control points. Each cycle of the

model culminates with a technical review that assesses

the status, progress, maturity, merits, risk, of

development efforts to date; resolves critical operational

and/or technical issues (COIs/CTIs); and reviews plansand identifies COIs/CTIs to be resolved for the next

iteration of the spiral.


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Risk AssessmentRisk Assessment

Spiral Model risk driven rather than document driven

The "risk" inherent in an activity is a measure of the

uncertainty of the outcome of that activity

High-risk activities cause schedule and cost overruns

Risk is related to the amount and quality of available

information. The less information, the higher the risk


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SummarySummary

Waterfall

good for budgeting, but doesnt analyze risk or have a

good way to manage errors found later in the process.

Iterative

Models attempt to solve this by coding as far as

possible, gathering feedback, and coding again..

Prototyping Plan to throw one away, then re-build it

right.

Incremental (Staged) Delivery Builds the software

by a series of waterfalls

Spiral:

Addresses Risk at every stage & let the stakeholders

determine the outcome.

Summary

mba 3rd spiral model

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