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Text of SDLC Concepts IVS Task Group SDLC – A Brief Introduction SDLC – A BRIEF INTRODUCTION...

  • Ground RulesPlease mute your mobile phonesStick to timelinessHelp each other in learning as learning is a continuous processPlease participate actively to make the session interactive:

  • Session ObjectivesLife Cycle of Software Development.Models of SDLCConcepts of various models of SDLC

  • At the End of Session you would be able to:

    What is SDLC?Various SDLC Models.Difference between SDLC and Exploratory models.

  • ContentsProduct, Process and MethodsMethodologies followed in late 60s for software DevelopmentWhat is SDLC?SDLC ModelsClassifications of SDLC ModelSequential ModelProgressive ModelIterative ModelSpiral modelOther ModelsDifferences between Exploratory & SDLC Models

  • Product, Process and Methods

    Product includes some of: hardware , software , documentation , installation, etc. ProcessProcess defines a framework for a set of key process areas that must be established for effective delivery of software engineering technology.involves all of: communication (internal and external) , standards (definition and adherence) , planning and monitoring , tools and methodologies , quality assurance Role of Processes Increasingly, software suppliers recognize that software development process capability is a key source of competitive advantage. Competition forces suppliers to improve processes to meet the conflicting demands of higher quality, lower cost, and compressed schedules. MethodMethods provides the technical how tos for building software

    SDLC ConceptsIVS Task Group

    Methodologies followed in late 60s for software DevelopmentMethodologies followed in late 60s for software Development

  • Methodologies followed in late 60s for software DevelopmentThe Software was developed on a Trial & Error basis.No Specific Process was followed during the development of the Product. Defects were detected only after the product is delivered to the external Users.This resulted in software crisisSoftware fail to meet user requirements.

    Softwares used to crash frequently.

    Development of Software became expensive.

    Software became difficult to alter, debug, and enhance.

    The Software was often delivered late.

    Software use resources non-optimally.

  • Some Root Causes for FailureInaccurate understanding of end-user-needsAd hoc requirements managementAmbiguous and imprecise communicationOverwhelming complexityUndetected inconsistencies in requirements, design and implementationsInsufficient testing resulting in late discovery of serious flawsPoor software qualityFailure to attack riskInsufficient use of automation tools

    SDLC ConceptsIVS Task Group

    Software Development Life Cycle (SDLC)Software Development Life Cycle (SDLC)

  • What is SDLC ?The various activities which are undertaken when developing software are commonly modeled as a software development lifecycle.The software development lifecycle begins with the identification of a requirement for software and ends with the formal verification of the developed software against that requirement.The software development lifecycle does not exist by itself, it is in fact part of an overall product lifecycle. Within the product lifecycle, software will undergo maintenance to correct errors and to comply with changes to requirements.The simplest overall form is where the product is just software, but it can become much more complicated, with multiple software developments each forming part of an overall system to comprise a product.

    SDLC ConceptsIVS Task Group

    SDLC - ModelsSDLC - Models

  • SDLC ModelsThere are a number of different models for software development lifecycles which explains the series of steps through which the product progresses. Life cycle models describe the interrelationships between software development phases. It specifies the relationships between project phases, including transition criteria, feedback mechanisms, milestones, baselines, reviews, and deliverables. Typically, a life cycle model addresses the following phases of a software project: requirements phase, design phase, implementation, integration, testing, operations and maintenance.

  • Importance of Lifecycle ModelsProvide guidance for project managementwhat major tasks should be tackled next? milestones!what kind of progress has been made?The necessity of lifecycle modelscharacter of software development has changedearly days: programmers were the primary usersmodest designs; potential of software unknownmore complex systems attemptedmore features, more sophistication greater complexity, more chances for errorheterogeneous users

  • Classifications of SDLC ModelSpiralIncremental

  • 1. Sequential ModelThe models used for the software development lifecycle have been sequential, with the development progressing through a number of well defined phases. The sequential phases are usually represented V Model Waterfall Model.

  • Different Phases of Sequential Model :Requirements phase - in which the requirements for the software are gathered and analyzed, to produce a complete and unambiguous specification of what the software is required to do Detailed Design phase - where the detailed implementation of each component is specified.Code and Unit Test phase - in which each component of the software is coded and tested to verify that it faithfully implements the detailed design.Software Integration phase - in which progressively larger groups of tested software components are integrated and tested until the software works as a whole.System Integration phase - in which the software is integrated to the overall product and tested.Acceptance Testing phase, where tests are applied and witnessed to validate that the software faithfully implements the specified requirements. Note: Software specifications will be products of the first three phases of this lifecycle model. The remaining four phases all involve testing the software at various levels, requiring test specifications against which the testing will be conducted as an input to each of these phases.

  • a. V ModelRequirement SpecificationsSystem TestingHigh Level DesignIntegrationTestingDetail DesignProgramSpecificationUnit TestingUser AcceptanceTestingCoding

  • b. Waterfall ModelRequirements SpecificationArchitectural DesignDetailed DesignCode and Unit TestingSoftware IntegrationSystem IntegrationAcceptance Testing

  • Advantages of Waterfall ModelEnforced discipline through documentsno phase is complete until the docs are done & checked by SQA groupconcrete evidence of progressTesting is inherent in every phasecontinuously as well as at end of phasesVerification of the Software is easy.

  • Drawbacks of Waterfall ModelDocument-driven modelcustomers cannot understand theseimagine an architect just showing you a textual spec!first time client sees a working product is after it has been coded. Problem here?leads to products that dont meet customers needsAssumes feasibility before implementationre-design is problematicworks best when you know what youre doingwhen requirements are stable & problem is well-known

  • 2. Progressive ModelA common problem with software development is that software is needed quickly, but it will take a long time to fully develop. The solution is to form a compromise between timescales and functionality, providing "interim" deliveries of software, with reduced functionality, but serving as a stepping stones towards the fully functional software. It is also possible to use such a stepping stone approach as a means of reducing risk.The usual names given to this approach to software development are progressive development or phased implementation. Within a progressive development lifecycle, each individual phase of development will follow its own software development lifecycle, typically using a V or waterfall model.

  • 2. Progressive Model - Structure Phase 1 DevelopmentPhase 2 DevelopmentFinal PhaseInterim Delivery 1Interim Delivery 2Final Delivery 2

  • 3. Iterative ModelAn iterative lifecycle model does not attempt to start with a full specification of requirements. Instead, development begins by specifying and implementing just part of the software, which can then be reviewed in order to identify further requirements. This process is then repeated, producing a new version of the software for each cycle of the model.RequirementsDesignImplementation and TestReview

  • 3. Iterative Model - Phases Requirements phase, in which the requirements for the software are gathered and analyzed. Iteration should eventually result in a requirements phase which produces a complete and final specification of requirements.Design phase, in which a software solution to meet the requirements is designed. This may be a new design, or an extension of an earlier design.Implementation and Test phase, when the software is coded, integrated and tested.Review phase - in which the software is evaluated, the current requirements are reviewed, and changes and additions to requirements proposed

  • 3. Spiral model

    The Spiral Model - an iterative (evolutionary) system development life cycle developed by Boehm (1988) which incorporates risk assessment.Developed in recognition of the fact that systems development projects tend to repeat the stages of analysis, design and code as part of the prototyping process.Model closely related to RAD, as it implies iterative development with a review possible after each iteration or spiral - which corresponds to the production of one prototype or incremental version.Spiral model includes best features of both the classic Waterfall SDLC and the Prototyping approach.

  • Spiral model contdEach spiral consists of four main activities:Planning: setting project objectives; defining alternatives; further planning on the next spiral; etc.Risk Analysis: analysis of alternatives & the identification & solution of risks. Development: designing, coding and testing etc. in increments.Evaluation: user evaluation of each spiral and then the final product.

  • Other SDLC Models UsedBuild and fix ModelIncremental ModelPrototyping ModelRapid Application Development Model

  • Lifecycle ModelsBuild-and-fixdevelop systemwithout specs or designmodify until customer is satisfiedWhy doesnt build-and-fix scale?changes during maintenancemost expensive!

  • Incremental ModelDivide project into buildseach adds new functionseach build integrated w/ structure & product tested as a wholeAdvantages ?operation product in weeksless traumatic to organizationsmaller capital outlayDisadvantages ?need an open architecturea big advantage come maintenance!too few builds build-and-fixtoo many builds overhead

  • Differences Between the Exploratory Style and Modern Software Development PracticesExploratory StyleSoftware developed on Trail and Error basisEmphasis on Error correctionErrors detected only during testingEmphasis only on coding during the entire development cycleReview at the end of the development phaseNo specific testing processLess attention was being given to producing good quality and consistent documentsInefficient planningModern Software DevelopmentUse of Life Cycle Models resulting in software development through several well-defined stagesEmphasis on detection of errors as close to their point of introduction as possible.Errors detected in each phase of developmentThe entire development cycle is divided into distinct phasesPeriodic reviews during each phase of development cycleSoftware testing has become systematicBetter visibility of design and code resulting in production of good quality and consistent and standard documentsThorough planning in terms of estimation schedulingmonitoring mechanisms

  • Questions?

  • Thank You!!IVS-TRAININGAny doubts or suggestions for improvement can be forwarded to: [email protected]