FMS SDLC Lecture 1

7/28/2019 FMS SDLC Lecture 1

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System System (from Greek Word systma,) is an organized

relationship among functioning units or components.

System is an orderly grouping of interdependentcomponents linked together according to a plan toachieve a specific objective.


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Characteristics Of Systems Organization: Implies the Structure and order. It is the arrangementof components to achieve objectives

Interaction: Refers to the manner in which each component functionswith other components of the system. (Ex computer)

Interdependence : Means that parts of the organization depends onone another.

Integration : It is concerned with how a system is tied together.

Central Objective : Each system works to achieve a common objective


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Elements Of a System Inputs :- material or information that enters a system

Outputs : - Outcome of Processing

Process : - Involves actual transformation of inputinto output

Contd


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Elements Of a System contd Control :- It is a decision making subsystem that

controls the pattern of activities governing input,process and output (Ex OS)

Feedback :- Control in dynamic system is achieved byfeedback. It may be positive (reinforce performance) or

negative (need action)

Contd


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Elements Of a System contd Environment : - Is the suprasystem within which an

organization operates.

Boundaries :- Limits that identify its components ,processing and its interrelationship (Ex ATM onlyWithdraw)


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Types Of System Physical or abstract systems

Open or closed systems

Man made systems


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Physical System : - Are tangible systems . Ex : -computer system

Abstract System :- are conceptual or nonphysicalentities . Ex: Model , Formula


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Open System :- Interacts with its environment

Closed System :- Do not Interact with itsenvironment . Is isolated from environmentalinfluences


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ManMade Information System : -An informationsystem (IS) is typically considered to be a set of interrelatedelements or components that collect (input), manipulate(processes), and disseminate (output) data and informationand provide a feedback mechanism to meet an objective.


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Major Information Systems are :-

Formal Information System

Informal Information System

Computer Based Information System


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Formal Information System : - Is Based on theorganization represented by the organization chart. Itis concerned with the pattern of authority andCommunication

Informal Information System :- It is an employee

based system designed to meet personnel needs and tosolve work related problems


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Computer-based Information System : -An InformationSystem is an organized combination of people, hardware, software,communication networks and the data resources that collects,transforms and disseminates information in a organization.


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INFORMATION

TECHNOLOGY

Hardware

Software

Databases

Networks

Other related

components

are used to build

INFORMATIONSYSTEMS

Payroll

System

Inventory

System

Marketing

System

Customer

Service

System

IS Vs IT


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Systems Development Life Cycle (SDLC) SDLC is the process of creating or altering systems, and the

models and methodologies that people use to develop thesesystems.

System life cycle is an organizational process of developing andmaintaining systems.

It helps in establishing a system project plan, because it givesoverall list of processes and sub-processes required for developing

a system.


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Steps of SDLC (Waterfall Model)Need

Recognition

Feasibility

Study

Requirement

Analysis

System

Design

Coding &Testing

Implemen-

-tation

Maintenance


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Need RecognitionWhat is the problem ?

One must know the problem before it is solved.

It leads to preliminary survey or initialInvestigation to determine whether an alternativesystem can solve the problem.


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Feasibility Study Depending on the results of the initial Investigation , thesurvey is expanded to a more detailed feasibility Study

It is a user oriented overview of the proposed informationsystems purpose and feasibility.


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Types Of Feasibility Economic Feasibility : - Involves questions such as whether

the firm can afford to build the information system , whetherbenefits exceeds costs.

Technical Feasibility :- - Involves questions such as whetherthe technology needed for the information system exists &whether the firm has enough experience using that

technology


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Organizational Feasibility : - Involves questions suchas whether the information system has enoughsupport to be implemented successfully

If the IS appears to be feasible , this phase produces afunctional specification (Formal Proposal)


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Formal Proposal consists of :-

Statement of the problem

Summary of findings & recommendations Details of findings

Recommendations & conclusions


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AnalysisAnalysis is a detailed study of the various operationsperformed by the system and their relationships withinand outside the system

It is a process of collecting factual data, understand theprocesses involved, identifying problems andrecommending feasible suggestions for improving thesystem functioning.

It determines whether or not a candidate system shouldconsider other related systems?


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Analysis Contd.. This involves studying the business processes, gatheringoperational data, understand the information flow, findingout bottlenecks and evolving solutions for overcoming theweaknesses of the system so as to achieve the organizational

goals.

System Analysis also includes subdividing of complexprocess involving the entire system, identification of data

store and manual processes.

DFD , Interview & Questionnaire are tools used in analysis


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System Design

Based on the user requirements and the detailed analysis of theexisting system, the new system must be designed.

System designing is the most crucial phase in the developments

of a system.

The design process translates requirements into arepresentation of the software that can be assessed for qualitybefore coding begins.


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DesignDesign focuses on four distinct attributes of a

program:

Data structure Database(Fields / types) Software architecture (Function Hierarchy)

Interface representations(Forms , reports, Screens)


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Coding The design must be translated into a machine-readable form.

The system design needs to be implemented to make it aworkable system.

This demands the coding of design into computerunderstandable language, i.e., programming language.

This is also called the programming phase


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Testing The testing process focuses on the logical

internals of the software ensuring that all

statements have been tested

Conduct tests to uncover errors and ensure thatdefined input will produce actual results thatagree with required results.


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Testing Unit Testing :- Test Each Program separately

System testing:- Test the functioning of the system as a whole. Ex:-Performance Test , Stress Test

Acceptance Testing :- User Acceptance Testing (UAT) is a processto obtain confirmation by the client that the modification oraddition meets mutually agreed-upon requirements. It is one of thefinal stages of a project and often occurs before a client or customer

accepts the new system. Types :Alpha Test (developer site) &Beta Test (Customer Site)


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Implementation Is the process of putting the system into operation in

an organization.

It includes training and conversion

Training : - Is the process of Ensuring that systemparticipants know what they need to know aboutsystem


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Conversion : - Different types of conversions are : -

Direct

Pilot

Parallel

Phased


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Direct Conversion :- involves an immediate conversionto the new system.

This method can appear cheaper but is full of problems.

If the new system is not working right it may mean lossof data which may have huge implications depending on

the type of data.

It is not recommended


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Parallel Conversion: Involves the old and new systemworking side by side.

Some operations are gradually implemented into the newsystem while the old system is still running.

After all the operations have been carried out under thenew system and the new system has been debugged then

the old system is discontinued.


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Phased Conversion: This involves the gradualimplementation of the new system.

As the various operations are tried on the new system ,the old is discontinued in those operations

Ex : If the system is introduced by functions , a newpayroll system might begin with hourly workers , thenadd salaried Employees


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Pilot Conversion: Involves implementing the newsystem in only a small part of the organization such assingle department .

If there are any problems with the new system then theold system is still there as a backup.

When it starts working smoothly it is installed in herest of the organization


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Maintenance Both users and technical specialists determines how well

it has met its objectives and decide whether any revisionis required or not .

Software will undoubtedly undergo change after it isdelivered to the customer

software must be adapted to accommodate changes in its

external environment or because the customer requiresfunctional or performance enhancements.


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Types Of Maintenance Corrective maintenance: modification of a software to correctdiscovered problems. It is used to correct errors in the system

Adaptive maintenance: It is used to make software product usablein a changed or changing environment. Adaptive maintenance isused to add enhancements (i.e. a new capability or feature) and isused to make the system easier to use.

Perfective maintenance: Is the modification of a software productto improve performance. Perfective maintenance can be used to

make an operational system more reliable and efficient.


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Strengths of SDLC Oldest and Most Widely Used

Simple

Step-by-step process Ensures consistency on sequence of phases and how

they are followed.

Distinct milestones and deliverables for each phase

Supports project management


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Weakness of SDLC Inflexible because real projects rarely follow thesequential f low that the model proposes

It is often difficult for the customers to state all

requirements explicitly.

The customer must have patience to wait to validate thesoftware product in the late phases. (until programs areimplemented)

Difficult to respond to changing customer requirements


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The Prototyping Model Often, a customer defines a set of general objectives for software

but does not identify detailed input, processing, or outputrequirements.

In other cases, the developer may be unsure of the efficiency ofan algorithm, the adaptability of an operating system, or the formthat human/machine interaction should take.

In these, and many other situations, aprototyping approachmayoffer the best solution.


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Prototype

L isten tocustomer

Customer

test-drives

Prototype

Build/revise

Prototype


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Steps of Prototype Identify basic requirements Determine basic requirements including the input and output

information desired. Develop Initial Prototype

The initial prototype is developed that includes only user interfaces. Review

The customers, including end-users, examine the prototype andprovide feedback on additions or changes.

Revise and Enhance the Prototype

Using the feedback both the specifications and the prototype canbe improved. Negotiation about what is within the scope of thecontract/product may be necessary.


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Types of prototyping Throwaway prototyping :-Also called close ended prototyping or RapidPrototyping .

Throwaway refers to the creation of a model that will eventually be discarded ratherthan becoming part of the final delivered software.

After preliminary requirements gathering is accomplished, a simple working model ofthe system is constructed to visually show the users what their requirements may looklike when they are implemented into a finished system.

The method used in building it is usually quite informal, the most important factorbeing the speed with which the model is provided.

The most obvious reason for using Throwaway Prototyping is that it can be done quickly


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Evolutionary prototyping :- builds a very robust prototype in astructured manner and is constantly refined .

The Evolutionary prototype, when built, forms the heart of the newsystem, and the improvements and further requirements will be built.

When developing a system using Evolutionary Prototyping, the system iscontinually refined and rebuilt.

Evolutionary Prototypes have an advantage over Throwaway Prototypes

in that they are functional systems. Although they may not have all thefeatures the users have planned, they may be used until the final systemis delivered.


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Incremental prototyping :- The final product is builtas separate prototypes. At the end the separateprototypes are merged in an overall design.


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Advantages Reduced time and costs: Prototyping can improve the quality ofrequirements and specifications provided to developers. Because changescost exponentially more to implement as they are detected later indevelopment, the early determination of what the user really wants canresult in faster and less expensive software

Customers can validate the prototype at the earlier stage and provide theirinputs and feedback

Improved and increased user involvement: Prototyping requires userinvolvement and allows them to see and interact with a prototype allowing them

to provide better and more complete feedback and specifications


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Good to deal with the following cases:

Customer can not provide the detailed requirements

Very complicated system-user interactions Use new technologies, hardware and algorithm

Develop new domain application systems


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Drawbacks Insufficient analysis: The focus on a limitedprototype can distract developers from properlyanalyzing the complete project.

User confusion of prototype and finished system:Users can begin to think that a prototype, intended tobe thrown away, is actually a final system that merely

needs to be finished or polished


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Developer attachment to prototype: Developers canalso become attached to prototypes they have spent agreat deal of effort producing it.

Excessive development time of the prototype: A keyproperty to prototyping is the fact that it is supposed tobe done quickly. If the developers lose sight of this fact,they very well may try to develop a prototype that is too

complex. When the prototype is thrown away the timespent is wasted

FMS SDLC Lecture 1

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