20100310 liwen waterfall
DESCRIPTION
waterfall modelTRANSCRIPT
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Waterfall Model
Speaker: Li-Wen Chen
Adviser: Quincy Wu
Date: 2010-03-10
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Outline
Waterfall ModelAdvantageDisadvantageConclusionReference
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Five additional features that must be added to this basic approach to eliminate most of the development risks. STEP 1: Program design comes first STEP 2: Document the design STEP 3: Do it twice STEP 4: Plan, control and monitor testing STEP 5: Involve the customer
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STEP 1: Program design comes first
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STEP 2: Document the design
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STEP 3: Do it twice
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STEP 4: Plan, control and monitor testing
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STEP 5: Involve the customer
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Six Distinct Phases
development proceeds sequentially through a series of phases Requirements analysis Design Implementation Testing Installation Maintenance
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Advantage
progress can be conclusively identified (through the use of milestones) by both vendor and client
ensures minimal wastage of time and effort
reduces the risk of schedule slippage, or of customer expectations not being met
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Disadvantage
It does not allow for much reflection or revision. Estimating time and costs with any degree of ac
curacy (as the model suggests) is often extremely difficult. customers don't really know what they want up-front
Designs that look feasible on paper turn out to be expensive or difficult in practice. re-design destroys the clear distinctions between phase
s of the traditional waterfall model a clear division of labor between, say, "designers", "prog
rammers" and "testers“ is neither realistic nor efficient in most software firms
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Waterfall development model considered harmful
In the early days of simple, stand-alone applications, the waterfall model worked well spawning a host of voluminous methodologies, but it does not suit the problems of the complex, risky, and integrated projects that IT has to deliver today.
Most of today's projects have a high proportion of reuse. The waterfall idea of creating a detailed set of requirements and then trying to find a package that fits is neither economic not practical.
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Conclusion
Whether you should use it or not depends largely on how well you believe you understand your custo
mer's needs how much volatility you expect in those needs a
s the project progressesThe model is recommended for use only in
projects which are relatively stable and where customer needs can be clearly identified at an early stage.
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Reference
Waterfall Model Managing the Development of Large Soft
ware Systems.
Waterfall model considered harmful Understanding the pros and cons of the
Waterfall Model of software development