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System Development LifecycleIntroduction to SDLCSystems Development Life Cycle (SDLC) adheres to important phases that are essential for developers, such as planning, analysis, design, testing and implementation.

There are several Systems Development Life Cycle Models in existence.

The oldest model, that was originally regarded as "the Systems Development Life Cycle" is the waterfall model: a sequence of stages in which the output of each stage becomes the input for the next.

2Contd..These stages generally follow the same basic steps but many different waterfall methodologies give the steps different names and the number of steps seem to vary between 4 (Testing) and 7 (Maintenance).

There is no definitively correct Systems Development Life Cycle model, but the steps can be characterized and divided in several steps

4The Systems Development Lifecycle (SDLC)Systems development life cycle (SDLC)Provides overall framework for managing systems development process

Two main approaches to SDLCPredictive approach assumes project can be planned out in advanceAdaptive approach more flexible, assumes project cannot be planned out in advanceAll projects use some variation of SDLC5Choosing the Predictive vs. Adaptive Approach to the SDLC

Initiation/PlanningTo generate a high-level view of the intended project and determine the goals of the project.

The feasibility study is used to present the project to upper management in an attempt to gain funding.

Projects are typically evaluated in three areas of feasibility: economical, operational, and technical.

It is also used as a reference to keep the project on track and to evaluate the progress of the MIS team. The goal of systems analysis is to determine where the problem is in an attempt to fix the system.

This step involves breaking down the system in different pieces and drawing diagrams to analyze the situation.

Analyze project goals, break down functions that need to be created, and attempt to engage users so that definite requirements can be defined.

Requirement Gathering requires individual/team from client as well as service provider side to get a detailed and accurate requirements.Requirements Gathering and Analysis Design In systems design functions and operations are described in detail, including screen layouts, business rules, process diagrams and other documentation.

The output of this stage will describe the new system as a collection of modules or subsystems.

The design stage takes as its initial input the requirements identified in the approved requirements document (SRS).

For each requirement, a set of one or more design elements will be produced as a result of interviews, workshops, and/or prototype efforts.

Contd.. Design elements describe the desired software features in detail, and generally include functional hierarchy diagrams, screen layout diagrams, tables of business rules, business process diagrams, and a complete entity-relationship diagram with a full data dictionary.

These design elements are intended to describe the software in sufficient detail that skilled programmers may develop the software with minimal additional input.

Build or coding Modular and subsystem programming code will be accomplished during this stage.

Unit testing and module testing are done in this stage by the developers.

This stage is intermingled with the next in that individual modules will need testing before integration to the main project.Testing The code is tested at various levels in software testing.

Unit, system and user acceptance testing are often performed.

This is a grey area as many different opinions exist as to what the stages of testing are and how much if any iteration occurs.

Types of testing:Data set testing. Unit testing System testing Integration testing Black box testing White box testing Module testing Regression testing Automation testing User acceptance testing ** Automation testing which is also known asTest Automation, is when the tester writes scripts and uses another software to test the software. This process involves automation of a manual process. Automation Testing is used to re-run the test scenarios that were performed manually, quickly and repeatedly.Apart from regression testing, Automation testing is also used to test the application from load, performance and stress point of view. It increases the test coverage; improve accuracy, saves time and money in comparison to manual testing.12Operations and maintenanceThe deployment of the system includes changes and enhancements before the decommissioning or sunset of the system.

Maintaining the system is an important aspect of SDLC. As key personnel change positions in the organization, new changes will be implemented, which will require system updates Management and control The Systems Development Life Cycle (SDLC) phases serve as a programmatic guide to project activity and provide a flexible but consistent way to conduct projects to a depth matching the scope of the project.

It is critical for the project manager to establish and monitor control objectives during each SDLC phase while executing projects.

Control objectives help to provide a clear statement of the desired result or purpose and should be used throughout the entire SDLC process.

Control objectives can be grouped into major categories (Domains), and relate to the SDLC phases as shown in the figure.

SDLC Phases Related to Management Controls Contd...To manage and control any SDLC initiative, each project will be required to establish some degree of a Work Breakdown Structure (WBS) to capture and schedule the work necessary to complete the project.

A work breakdown structure (WBS) in project management and systems engineering, is a tool used to define and group a project's discrete work elements (or tasks) in a way that helps organize and define the total work scope of the project

The WBS and all programmatic material should be kept in the Project Description section of the project notebook.

The WBS format is mostly left to the project manager to establish in a way that best describes the project work. Strengths of SDLCControl.Monitor Large projects.Detailed steps.Evaluate costs and completion targets.Documentation.Well defined user input.Ease of maintenance.Development and design standards.Weakness of SDLCIncreased development time.

Increased development cost.

Systems must be defined up front.

Hard to estimate costs & project overruns.

User input is sometimes limited.18Waterfall ModelThe waterfall model is a sequential software development process, in which progress is seen as flowing steadily downwards (like a waterfall) through the phases of Initiation, Analysis, Design (validation), Construction, Testing and maintenance

The first formal description of the waterfall model is often cited to be an article published in 1970 by Winston W. Royce (19291995).

MaintenanceWaterfall Model** Unit Testing. It is also called Component Testing. It is performed on standalone module to check it is developed correctly. The goal of unit testing is to isolate each part of the program and show that the individual parts are correct. Unit testing is usually performed by the developer.

2021Waterfall ModelProgresses through the orderly sequence of steps

It assumes that each subsequent phase will begin when activities in the current phase have been completed.

Each phase has defined entry and exit criteria

Transition from one phase to the next is accomplished by passing a formal review,

Passing the review indicates an agreement among the project team members and the customer that the phase has ended and the next one can begin2122Waterfall Model - StrengthsThe model is well known by non-software customers and end users

It tackles complexity in an orderly way, working well for projects that are well understood but still complex.

It is easy to use as development proceeds one phase after another

It provides structures to a technically weak or inexperienced staff

It works well when quality requirements dominate costs and schedule requirements

It defines quality control procedures. Each deliverable is reviewed as it is completed

It is easy to track the progress of the project using a Gantt Chart2223Waterfall Model - WeaknessesIt has an inherently linear sequential nature - any attempt to go back two or more phases to correct a problem or deficiency results in major increases in cost and schedule

It can present a false impression of status and progress - 35 percent done is a meaningless metric for the project manager

Integration happens in one big bang at the end. With a single pass through the process, integration problems usually surface too late.

Tight Mgt. & control is needed because there is no provision for revising the requirements

Insufficient opportunity for a customer to preview the system until very late in the life cycle2324When to use Waterfall Model The Waterfall model performs well for product cycle with a stable product definition and well-understood technical methodologies.

If a company has experience in building a certain type of system like accounting, payroll, compilers etc., then a project to build another of the same type of product, perhaps even based on existing designs, could make efficient use of the waterfall model.

Another example of appropriate use is the creation and release of a new version of an existing product, if the changes are well defined and controlled.2425Newer Adaptive Approaches to the SDLCIteration Work activities are repeated Each iteration refines previous resultApproach assumes no one gets it right the first timeThere are a series of mini projects for each iteration

Based on spiral modelProject cycles through development activities over and over until project is completePrototype created by end of each cycleFocuses on mitigating risk26 Incremental Process Model Incremental model is an evolution of waterfall model.

Theincrementalbuild modelis a method of software development where the model is designed, implemented and tested incrementally (a little more is added each time) until the product is finished.

It involves both development and maintenance. The product is defined as finished when it satisfies all of its requirements.26

Contd.. Incremental software development model may be applicable to projects where:

Software Requirements are well defined, but realization may be delayed.

The basic software functionality are required early

28Iteration of System Development Activities

29The Incremental Model

2930The Incremental Model The incremental development is the process of constructing a partial implementation of a total system and slowly adding increased functionality or performance.

Incremental model describes the process of prioritizing requirements of the system and then implementing them in groups.

Each subsequent release of the system adds function to the previous release, until all designed functionality has been implemented.30Contd.. The product is decomposed into a number of components, each of which are designed and built separately (termed as builds).

Each component is delivered to the client when it is complete. This allows partial utilization of product and avoids a long development time.

32The Incremental Model Approach..The early phases of the life cycle (Planning, Analysis & Design) consider the entire system to be developed.

During these phase, the increments and the functions within them are defined for development. Each increment then proceeds through the remaining phases of the life cycle code, test and delivery.

A set of functions that are the core, or highest priority requirements critical to the success of the project, or that will reduce risks is constructed, tested and implemented first.

3233Strengths-The Incremental Model Funds for a total product development need not be expended up-front because a major function or high-risk function is developed and delivered first.An operational product is delivered with each increment.Lessons learned at the end of each incremental delivery can result in positive revisions for the next; the customer has an opportunity to respond to each buildThe divide and conquer rule allows the problem to be broken down into manageable pieces.Limited staff can be used, with the same team working sequentially to deliver each increment.Risk is spread across several smaller increments instead of concentrating in one large development3334Weaknesses: Incremental Model The definition of a complete, fully functional system must be done early in the life cycle to allow for the definition of the increments

Well-defined interfaces are required because some modules will be completed long before others

Formal reviews and audits are more difficult to implement on increments than on a complete system

The customer must realize that the total cost will not be lower

It requires good planning and design; Management must take care to distribute the work; the technical staff must watch dependencies3435When to use: Incremental Model When most of the requirements are understood up-front but are expected to evolve over time;

On projects that have lengthy development schedules, usually over one year

On low-to-medium-risk programs

On a project with new technology, allowing the user to adjust to the system in smaller incremental steps rather than leaping to a major new product

When it is too risky to develop the whole system at once

3536The RAD Model Rapid Application Development (RAD) is an incremental software development process model that emphasizes a very short development cycle [typically 60-90 days].

If requirements are well understood and project scope is constrained, the RAD process enables a development team to create a fully functional system within very short time period

The RAD model is a high-speed adaptation of the waterfall model, where the result of each cycle a fully functional system.3637Phases of The RAD Model Business Modeling: The information flow among business functions is defined by answering questions like what information drives the business process, what information is generated, who generates it, where does the information go, who process it and so on.

Data Modeling:The information collected from business modeling is refined into a set of data objects (entities) that are needed to support the business. The attributes (character of each entity) are identified and the relation between these data objects (entities) is defined.

3738Phases of The RAD Model Process Modeling:The data object defined in the data modeling phase are transformed to achieve the information flow necessary to implement a business function. Processing descriptions are created for adding, modifying, deleting or retrieving a data object.

Application Generation:Automated tools are used to facilitate construction of the software; even they use the 4th GL techniques.

Testing and Turn over:Many of the programming components have already been tested since RAD emphasis reuse. This reduces overall testing time. But new components must be tested and all interfaces must be fully exercised.

3839The RAD Model

3940Strengths of The RAD Model Cycle time for the full product can be reduced due to the use of powerful development tools

Fewer Developers are required because the system is developed by a project team familiar with the problem

Quick initial view of the product are possible

Ongoing customer involvement minimizes the risk of not achieving customer satisfaction and ensures that the systems meets the business needs and that the operational utility of the product is sound4041Weaknesses of The RAD Model If the users cannot be involved consistently throughout the life cycle, the final product will be adversely affected

This model requires highly skilled and well-trained developers in the use of the chosen development tools to achieve the rapid turnaround time

It can fail if reusable components are not available

It requires developers and customers who are committed to rapid-fire activities in an abbreviated time-frame

There is a risk of never achieving closure - the project manager must work closely with both the development team and the customer to avoid infinite loop.4142When to use the RAD Model On Systems that may be modularized and that are scalable

On systems with reasonable well-known requirements

When the end user can be heavily involved throughout the life cycle

On projects requiring short development times, usually about 60 days

When reusable parts are available through automated software repositories42** scalabilityis the ability of a system, network, or process, to handle a growing amount of work in a capable manner or its ability to be enlarged to accommodate that growth.Prototyping Model The Prototyping Model is a systems development method (SDM) in which aprototype(an early approximation of a final system or product) is built, tested, and then reworked as necessary until an acceptable prototype is finally achieved from which the complete system or product can now be developed. This model works best in scenarios where not all of the project requirements are known in detail ahead of time.

It is an iterative, trial-and-error process that takes place between the developers and the users.Contd..A prototype acts as a sample to test the process. From this sample we learn and try to build a better final product.

Please note that this prototype may or may not be completely different from the final system we are trying to develop.

Need of Prototyping ModelThis type of System Development Method is employed when it is very difficult to obtain exact requirements from the customer(unlike waterfall model, where requirements are clear).

While making the model, user keeps giving feedbacks from time to time and based on it, a prototype is made.

Completely built sample model is shown to user and based on his feedback, the SRS(System Requirements Specifications) document is prepared. After completion of this, a more accurate SRS is prepared, and now development work can start using Waterfall Model.

Steps in the Prototyping Model There are several steps in the Prototyping Model:The new system requirements are defined in as much detail as possible. This usually involves interviewing a number of users representing all the departments or aspects of the existing system. A preliminary design is created for the new system. A first prototype of the new system is constructed from the preliminary design. This is usually a scaled-down system, and represents an approximation of the characteristics of the final product.

Contd..4. The users thoroughly evaluate the first prototype, noting its strengths and weaknesses, what needs to be added, and what should to be removed. The developer collects and analyzes the remarks from the users.

5. The first prototype is modified, based on the comments supplied by the users, and a second prototype of the new system is constructed.

6. The second prototype is evaluated in the same manner as was the first prototype.

Contd.. 7. The preceding steps are iterated as many times as necessary, until the users are satisfied that the prototype represents the final product desired.

8. The final system is constructed, based on the final prototype.

9. The final system is thoroughly evaluated and tested. Routine maintenance is carried out on a continuing basis to prevent large-scale failures and to minimize downtime.

Prototyping Processing ModelAdvantages of Prototyping Model1)When prototype is shown to the user, he gets a proper clarity and 'feel' of thefunctionalityof the software and he can suggest changes and modifications.

2)This type of approach of developing the software is used for non-IT-literate people. They usually are not good at specifying their requirements, nor can tell properly about what they expect from the software.

3)When client is not confident about the developer's capabilities, he asks for a small prototype to be built. Based on this model, he judges capabilities of developer.

Contd..4)Sometimes it helps to demonstrate the concept to prospective investors to get funding for project.

5)It reduces risk of failure, as potential risks can be identified early and mitigation steps can be taken.

6)Iteration between development team and client provides a very good and conductive environment during project.

7)Time required to complete the project after getting final the SRS reduces, since the developer has a better idea about how he should approach the project.Disadvantages of Prototyping Model1)Prototyping is usually done at the cost of the developer. So it should be done using minimal resources. It can be done using Rapid Application Development (RAD) tools. Please note sometimes the start-up cost of building the development team, focused on making prototype, is high.

2)Once we get proper requirements from client after showing prototype model, it may be of no use. That is why, sometimes we refer to the prototype as "Throw-away" prototype.

3)It is a slow process.

4)Too much involvement of client, is not always preferred by the developer.

5)Too many changes can disturb the rhythm of the development team.

53Spiral Model Originally proposed by Berry Boehm in 1988Process is represented as a spiral rather than as a sequence of activities with backtracking

Each loop in the spiral represents a phase in the process.

This model of development combines the features of the prototyping model and thewaterfall model. The spiral model is intended for large, expensive and complicated projects.

53Software engineering principles & practice, Wiley, page 63Contd..The iterations were typically 6 months to 2 years long.

Each phase starts with a designgoaland ends with the client(who may be internal) reviewing the progress thus far.

Analysis andengineering efforts are applied at each phase of the project, with an eye toward the end goal of the project.55

55Steps in Spiral ModelThe steps in the spiral model iteration can be generalized as follows:-The system requirements are defined in as much detail as possible. This usually involves interviewing a number of users representing all the external or internal users and other aspects of the existing system.

A preliminary design is created for the new system. This phase is the most important part of "Spiral Model". In this phase all possible (and available) alternatives, which can help in developing a cost effective project are analyzed and strategies to use them are decided.

This phase has been added specially in order to identify and resolve all the possible risks in the project development. If risks indicate any kind of uncertainty in requirements, prototyping may be used to proceed with the available data and find out possible solution in order to deal with the potential changes in the requirements.

Contd.. A firstprototypeof the new system is constructed from the preliminary design. This is usually a scaled-down system, and represents an approximation of the characteristics of the final product.

A second prototype is evolved by a fourfold procedure:evaluating the first prototype in terms of its strengths, weaknesses, and risks;defining the requirements of the second prototype;planning and designing the second prototype;constructing and testing the second prototype.

58Spiral Model Spiral Model is cyclic in nature

Each cycle of the spiral consists of four stages, and each stage is represented by one quadrant

5859Spiral model of the software processRiskanalysisRiskanalysisRiskanalysisRiskanalysisProto-type 1Prototype 2Prototype 3Opera-tionalprotoypeConcept ofOperationSimulations, models, benchmarksS/WrequirementsRequirementvalidationDesignV&VProductdesignDetaileddesignCodeUnit testIntegrationtestAcceptancetestServiceIntegrationand test planDevelopmentplanRequirements planLife-cycle planREVIEWProgress through stepsCommulative CostDetermine Objectives, alternatives, constraintsEvaluate alternatives, Identify, resolve risksDevelop, verify next-level productPlan next phasesCommitment Ratio5960Spiral Model Quadrant 1 : Determine Objectives, alternatives and constraints Objectives such as performance, functionality, ability to accommodate change, hardware/software interface, and critical success factors are identified.

Alternative means of implementing this portion of the product are determined constraints imposed on the application of the alternatives (cost, schedule, interface, environmental limitations, etc.) are determined

Risks associated with lack of experience, new technology, tight schedules, poor processes and so on are documented60** Critical success factor(CSF) is the term for an element that is necessary for an organization or project to achieve its mission. It is a critical factor or activity required for ensuring the success of a company or an organization.61Spiral Model Quadrant 2 : Evaluate alternatives, and identify and resolve risks

Alternatives relative to the objectives and constraints are evaluated

The identification and resolution of risks (risk management, cost-effective strategy for resolving sources, evaluation of remaining risks where money could be lost by continuing system development etc. ) occurs61Software engineering principles & practice, Wiley, page 6362Spiral Model Quadrant 3 : Develop Next Level ProductTypical activities in this quadrant could be Creation of a design,Review of DesignDevelopment of codeInspection of CodeTesting and packaging of the product.

The first build is the customers first look at the system.

With each subsequent build, a better idea of customer requirements is developed. 62Software engineering principles & practice, Wiley, page 6363Spiral Model Quadrant 4 : Plan Next PhaseTypical activities in this quadrant could be Development of the Project PlanDevelopment of the configuration Management planDevelopment of the test plan development of the installation plan63Software engineering principles & practice, Wiley, page 6364Spiral Model : StrengthsThe spiral model allows users to see the system early, through the use of rapid prototyping in the development life cycle

It allows users to be closely tied to all planning, risk analysis, development and evaluation activities

It splits a potentially large development effort into small chunks in which critical, high-risk functions are implemented first, allowing the continuation of the project to be optional - Advantage of Incremental release64Software engineering principles & practice, Wiley, page 6365Spiral Model : StrengthsIt provides early and frequent feedback from users to developers, ensuring a correct product with high quality

Management control of quality, correctness, cost schedule, and staffing is improved through review at the conclusion of each iteration

It provides productivity improvement through reuse capabilities

All money needed for the project need not be allocated up-front

Cumulative costs may be assessed frequently and a decrease in risk is associated with the cost65Software engineering principles & practice, Wiley, page 6366Spiral Model : WeaknessesIf the project is low-risk or small, this model can be an expensive one. The time spent evaluating the risk after each spiral is costlyThe model is complex and developers, managers and customers may find it too complicated to useConsiderable risk assessment expertise is requiredThe spiral may continue indefinitely, generated by each of the customers responses to the build initiating a new cycle -closure may be difficult to achieveIt can be hard to define objective, verifiable milestones that indicate readiness to proceed through the next iterationThe challenge for software teams and their managers is to establish a proper balance between the critical project and product parameters and customer satisfaction66Software engineering principles & practice, Wiley, page 6367When to use Spiral ModelFor projects that represent a medium to high risk

When it is unwise to commit to a long-term project due to potential changes in economic priorities and when these uncertainties may limit the available time frame

When it is important to focus on stable or known parts while gathering knowledge about changing parts.

When new technologies are being employed, such as first-time object oriented approaches

67Software engineering principles & practice, Wiley, page 6368Tools and TechniquesTools

Software support that helps create models or other required project components Range from simple drawing programs to complex CASE (Computer Aided software Engineering) tools to project management software

Techniques

Collection of guidelines that help analysts complete a system development activity or taskCan be step-by-step instructions or just general advice** Computer-aided software engineering(CASE) is the scientific application of a set of tools and methods to asoftwaresystem which results in high-quality, defect-free, and maintainable software products.6869Some Tools Used in System Development

70Some Techniques Used in System Development

END OF Chapter SDLC