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I.T. for Management

CHAPTER-15

System Development Cycle (SDLC)

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System Development Cycle (SDLC)

System Development typically goes thru several stages in the entire lifespan right from analysis, design, implementation.Water Fall methodThe Water Fall method is one of the most commonly used lifecycles for developing software solutionsIn the Waterfall method a large module is broken down into small and manageable modulesOne of the most important limitation of the Waterfall model is that there is no scope for going back from the next to the previous stage

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System Development Cycle (SDLC)

Water Fall method

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Water Fall method• With waterfall development-based methodologies, the

analysts and users proceed sequentially from one phase to the next.

• The two key advantages of waterfall development-based methodologies are:

- The system requirements are identified long before programming begins.

- Changes to the requirements are minimized as the project proceeds.

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Water Fall method.• The two key disadvantages of waterfall development-

based methodologies are:- The design must be completely specified before

programming begins.- A long time elapses between the completion of

the system proposal in the analysis phase and the delivery of the system.

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Incremental /evolutionary ModelsThe incremental approach believes in looking at the smaller portions of a software systemIn the incremental approach there is a constant flow of delivered software products to the end userConsider increment in following example

1stincrement We begin developing small solution which can print an invoice

2nd increment Generates Sales register& sales analysis3rd increment Enter & print receipt of money4th increment Generate collection report

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Incremental /evolutionary ModelsFrom above example we can see how application can grow over a period. The incremental approach considerably reduces the risk in software successThe incremental approach believe in Revisiting previously developed increments With 3rdgeneration languages like COBOL, incremental models were almost unthinkable

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System Development Cycle (SDLC)

Incremental /evolutionary Models

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Some popular incremental models areSpiral modelHere the software goes thru a phase of analysis, risk assessment, design & coding before moving to the next phaseThus each cycle leads to an increase in functionality of the softwareThe advantages of spiral model is also that the requirement & risk of the software are revisited in every cycle& that too for the entire development cycle

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Prototyping• Prototyping-based methodologies perform the

analysis, design and implementation phases concurrently.

• All three phases are performed repeatedly in a cycle until the system is completed.

• A prototype is a smaller version of the system with a minimal amount of features.

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Prototyping

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Prototyping• Advantage: Provides a system for the users to

interact with, even if it is not initially ready for use.

• Disadvantage: Often the prototype undergoes such significant changes that many initial design decisions prove to be poor ones.

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Throwaway Prototyping• Throwaway prototyping methodologies are

similar to prototyping based methodologies.• The main difference is that throwaway

prototyping IS completed during a different point in the SDLC.

• Has relatively thorough analysis phase.

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• RAD-based methodologies adjust the SDLC phases to get some part of system developed quickly and into the hands of the users.

• Most RAD-based methodologies recommend that analysts use special techniques and computer tools to speed up the analysis, design, and implementation phases, such as CASE (computer-aided software engineering) tools.

• One possible subtle problem with RAD-based methodologies is managing user expectations

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Software Lifecycle and OOAD

• The SDLC is composed of four fundamental phases:

- Planning- Analysis- Design- Implementation

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• Each of the phases include a set of steps, which rely on techniques that produce specific document files that provide understanding about the project.

• To Understand the SDLC:- Each phase consists of steps that lead to specific

deliverables- The system evolves through gradual refinement

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Software Maintenance PhaseWhile most software lifecycles focus on the development of software product, it is known fact in the industry the cost spent on maintaining software is always more than the cost of originally developedHence maintenance is one of important phase of software developmentGood structure, reusable component, good practice in version control & keeping tracks of changes makes maintenance easy task

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End of Chapter 15

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