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Transcript of SDLC_DOCU
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Prof. DG JHA
System Development Process
Systems development refers to the process of examining a business situation with the
aim of improving it through stream-lined procedures and methods. Systems
development process can be broadly thought of as combination of two components
Systems Analysis and Systems Design.
Systems Design is the process of planning a new business system or one to replace or
complement an existing system.
Systems Analysis is the process of gathering and interpreting facts, diagnosing
problems, and using the information to recommend improvements to the system.
This is the job of Systems Analysts. The major responsibilities of a Systems Analysts
are
Defining requirements for improving or replacing the existing information
system Ensuring cost-effectiveness of recommendations
Guiding systems development and implementation activities
Designing system flow and procedures to ensure control and security of data
Testing system segments to ensure adequacy in meeting requirements.
Systems Development Life Cycle (SDLC) Methodology:
System Development Life Cycle (SDLC) methodology is a traditional
development methodology that consists of a set of development activities that
have a prescribed order.
Once a problem or an opportunity for a new system is recognized, a request
for development of the system is forwarded to planners. If approved and
scheduled for development, a study is conducted to ensure that the proposed
information system is feasible. The specification of the system requirements
follows. Then come the System design, implementation, testing, conversion
and evaluation. After the system evaluation, a recycling of development of
activities may occur if problems that call for system modifications and/or
redevelopment get identified. The term development cycle is used to
acknowledge the importance of recycling in meeting the information needs.
SDLC is the standard methodology followed at the time of development of
information systems. One reason for which it is still favored is that a SDLC
provides for project control and has logical order, with the output of each stage
serving as an input for the next.
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SDLC STAGE 1: Initiating A Development Request
Once the need for an information system is identified within an organization
a request for development of the system is forwarded to the person/s in the
organization responsible for planning. A manager of a functional department,
operational personnel, customers, unions or computer specialists may initiate
a development request it sometimes gets originated through a suggestionbox too.
Most companies have a planning officer or special section often called MIS committee
that evaluates the requests for new system, to approve decisions and to establish
development priorities.
SDLC STAGE 2: Planning
Planners while deciding upon long and short range planning objectives take into
consideration: -
Corporate goals
Available resources
Organizational constraints
Technological trends
Competitive environment
SDLC STAGE 3: Feasibility Study
A feasibility study determines whether a computerized information system can be
implemented to generate the desired output, given the organizational constraints.
Also, alternative solutions to the information problem are examined and ranked
during the study.
In addition, the cost of the proposed information system, in terms of both monetary
and benefits is estimated. Proposed problem solutions are tested against the
following constraints: -
1. Economic feasibility
Economic feasibility is conceptually simple if the expected benefits of a
proposed solution are equal to or exceed the expected cost, the solution can be
judged as economically feasible.
In practice however, both sides of this equation are difficult to calculate during a
feasibility study. The reasons could be
User requirements are not fully formulated at this stage
Preliminary cost estimates are often unreliable It is therefore perceived that
the benefits of the solution are higher than the cost. Its savings that often
matters the most while determining the feasibility of a particular solution.
The implementation of an information system could very well result in cost
reduction. It could be
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Reduction of operation cost or clerical personnel
Absorption of routine administrative functions thereby increasing the
efficiency
A cost-benefit analysis is also done to determine the economic feasibility.
The primary objective of the cost-benefit analysis is to find whether it iseconomically worthwhile to invest in the project i.e., if the return on
investment is good, then the project is considered economically worthwhile.
Cost-benefit analysis is performed by listing down all the cost associated
with the project. Cost can be classified into direct and indirect costs.
Direct costs are those incurred in
Buying equipment
Employing people
Rent etc.
Indirect costs are those involving Problem time spent by user in discussing problems
Gathering data about the problem etc.
The benefits can be classified into
Tangible Benefits Intangible Benefits
Direct savings made due to reducing-
inventories, delays in collecting
outstanding payments, cost of
production etc.
Better service to customers.
Savings due to reduction in manpower
or increasing volume of work with thesame manpower.
Superior quality of products etc.
The sum of all cost is compared with sum of all savings. But it is not always easy
to ascertain intangible benefits.
2. Financial feasibility
Often a proposed system may sound economically feasible, but the firm may lack
sufficient capital to support implementation of the system. It is important that the
study team determine the financial feasibility at this stage i.e., the availability of
funds to finance systems developments.
Study teams often consider the economic and financial constraints together and
issue a single decision on economic and financial feasibility.
Financial feasibility is based on information provided by personnels in the finance
section of the organization, who decide on Whether the money is to be borrowed,
or whether internal financing will suffice, or whether the combining of both is
required. Capital budgeting decisions in large firms generally require complex
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calculations to determine relative merits of project competing for funds. In such cases,
it becomes difficult for the management to decide between allocation of limited
financial resources to research and development, to plant renovation, to staff
expansion, to the development of new information system or to other projects and at
the same time achieve the target rate of investment.
3. Organizational feasibility
Proposed solutions must also be tested against organizational constraints
Does the company have the adequate staff to implement the new system?
Will the employees support the system or resist it?
If any organizational constraint exist then the employees may have to
Alter their work patterns
Accept some experimentation
Work in an atmosphere of change
Acquire administrative and technical skills to implement the system
The most important factor in testing the organizational feasibility is the attitude of
the management towards the proposed system. If the management believes that the
system will not contribute to business objectives and is a waste of corporate
resources, they will not give the system the support needed to make it a success.
4. Technological feasibility
Sometimes the solutions may not be feasible due to technological constraints. For
Example, an information system that requires reliable, inexpensive equipment to
read handwriting is not feasible at times because devices meeting this requirement
may not be available in the market.
The technological considerations take into the account whether the necessary
hardware, software and application tools are available for the desired solution
under study.
Often there may be risk or probability factor involved, the
elements/equipments/devices may be future items promised but yet not available.
It therefore becomes essential for the management to check
The reliability of the vendor claims
Whether the particular item is on the critical path
Insurance in case of late delivery
Each of the items required must be carefully evaluated to ascertain its relevance in
information system development. Higher the dependence on sophisticated
technological items; the greater is the risk factor in selecting a particular application
for development. It is up to the committee to determine whether the technological
limitations such as these exist for the problem at hand.
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5. Operational feasibility
Quite often, operational feasibility is most overlooked element in the entire
feasibility analysis. Operational feasibility is whether the proposed solution can fit
in with existing operations. A particular solution may look technically and
economically feasible but may fail to produce the forecasted benefits because of the
fact that the company is unable to make it functional.
It is necessary to assess management, non-management and general operational
considerations. The major focus of the application must be ascertained and
resulting impact on the top, middle and operational management must be analyzed.
6. Other feasibility consideration
While doing feasibility analyses it is important to consider the internal as well as
external constraints. The information system will have little or no value unless they
are completed as per the schedule.
The results of the feasibility study are forwarded to the corporate managementalong with the recommendation to continue or discontinue the project. The final
decision whether to proceed to next phase or not rests with the corporate
management.
If the management agrees with committees recommendations and decides to
proceed with the system development. The following steps are initialized
A budget for the project is authorized
A development schedule for the project is prepared
The long run operational plans and development schedules are updated
Development policies and procedures are framed
Development personnel are selected, including the project leader.
SDLC STAGE 4: Specifying System/User Requirements
This phase concentrates on defining the system objectives and formulating the
specifications for the information system under development. A system
requirements statement is prepared that outlines
Reports to be generated
Processes to be performed
Inputs needed
Resources required
Procedures to be followed
This acts as a framework for the design of the new system
Corporate management may decide to terminate the project after reviewing the
system requirement document. Some of the reasons why the project may be shelved
at this stage could be-
Management dissatisfaction with the specifications
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Estimated costs going higher
Unavailability of expected resources
Revised corporate priorities
SDLC STAGE 5: System Design
During the system design, the analysts draw up entire operational plan. The model(mathematical representation) and algorithm (step-by-step process) to be used in the
problem solution is selected. The database is designed. Hardware costs, capability,
speed, error rates and other performance characteristics are specified. Changes to
be made up in the organizational structure are outlined. Input/Output files, forms
and procedures are planned. Finally, standards for listing, documentation and
system control are formulated.
SYSTEM ANALYSIS v/s SYSTEM DESIGN
When a computerized information system is under development, analysis activities
are called systems analysis. The environment in which the system will operate is
studied, the problems are identified, and the tasks that need to accomplished aredetermined. The specification of users need is the objective of this study.
What is done during the system analysis?
Obtain functional specification based on revised user requirement and feasibility
analysis.
End product of system analysis phase
Functional specification
Budget schedule
Physical requirement such as storage and processor
The design phase, called system design consists of planning the use of information
technology to meet users specifications.
What is done during the system design?
Logical design of programs
Design of database
Test and implementation plan
End product of system analysis phase
Logical design of database, programs and test plans
SDLC STAGE 6: System Implementation
The most important part in the implementation of a computerized information
system isprogramming.
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The implementation activity also include
Database organization i.e., creating new files or restructuring the old. The
collection, verification and storage of additional data may also be required if
the needed data doesnt already exist in the corporate database.
Systems orientation and training: it becomes essential for the operating
personnels to get tuned with the development process as they are the peoplewho are expected to use this system when it goes online.
Preparation of manuals and documentation of procedures.
SDLC STAGE 7: Testing The Solution
Once the programs are written, procedure developed, organizational changes
implemented, data collected and hardware installed, the new system gets ready for
testing. Testingand debuggingare vital steps in developing computer programs. In
general, testing is the process of making sure the program performs as intended;
debugging is the process of locating and eliminating errors.
During testing the actual performance of the system is compared with the desiredsystem performance. The common testing methods include pilot testing, parallel run
and simulation techniques.
The sequence in which the testing activities normally occur is
Unit Testing
(Testing of Individual programs)
Volume Testing
(Testing the application for large
amount of data)
Acceptance Testing
(Conducting any tests required by
the user)
Unit Testing and Acceptance Testing The main purpose of testing an information system is to find errors and correct
them. A successful test is one that finds an error.
Once the modules are developed, the unit testing is carried out to confirm data
transaction and outputs validity and accuracy. In this testing, transaction level
processes are checked to confirm the input-process-output relation, and the data
storage and the transaction level updating.
System Testing
(Testing the entire system ofprograms)
Integration Testing
(Testing all related sub-systems
together)
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When the unit testing is over and module level processes are confirmed, the modules
are put together to generate the information as determined in the requirement
definition. The process of putting the modules together is a process of integration. It
is intended to produce the results of data integration.
The system so developed is tested as a whole for several aspects such as information
quality, performance, utility, user acceptance and so on.
Once the system testing is complete, the system is implemented at site, on the
hardware and software platform. The system implementation step has its own
procedure starting from installation of hardware and software, training the users,
and then shifting to fully designed system.
While implementing the system minor modification and/or adjustment may be
required for ease of acceptance by the user. The system is designed keeping this
natural requirement in post implementation stage. A good system design and itsimplementation has higher user acceptance because it helps solve the problem in
business performance, and meets the information need, within a stipulated time
frame, with an assured quality and security of information.
System Testing
System-level testing is one of the most essential components before installation of an
information system. It involves-
a) Preparation of realistic test data in accordance with the system test plan,
b) Processing the test data using new equipment,
c) Thorough checking of the results of all system tests, andd) Reviewing the results with future users, operators and support personnel.
System-level testing is an excellent time for training employees involved in the
operation and maintenance of Information System.
Alpha and Beta Testing
If software is developed as a product for many customers, it may not meet the
specific requirements of a typical customer. Normally the group of experts having
the definite skill set is invited to carry out the test at the developers site to identify
deviations and/or error with respect to the customers need, it is called Alpha
testing. The tests are carried out under the developers controlled environment.
Users of the software do theBeta testingof software at the customers site. The users
then record the problems and suggest the modification that can be incorporated by
the developer.
Unsatisfactory test may results in recycling i.e., repetition of one or more phases
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of development in order to correct poor performance of the system. It may
require any or all of the following
Redesign
Change in the data flow
Replace equipment
Debug program Make other adjustment with the system
The need for recycle is normal and should be expected.
SDLC STAGE 8: Conversion
When the testing results are favorable, conversion takes place. The newly developed
procedures, manuals, forms, files, software and equipment are placed in operation.
When a system is replacing an existing one, its implementation becomes critical.
There are four major types of conversion strategies: -
Parallel Conversion
- Old and new system run parallel till new system becomes reliable- Costly but safe approach- Best suited for critical applications
Direct (Changeover) Conversion
- Old system is replace by a new system- Less costly but more risky as compared to parallel approach
- Best suited to non-critical applications
Modular Prototype Conversion (Pilot Study)
- One department or unit is testing ground- Good for system that is moderately critical
Phased Conversion
- New system is slowly incorporated into the operational environment
- Safe and conservative approach- Well suited to critical applications
The entire set of activities and sub activities from feasibility study through to
conversion needs planning and co-ordination. This is also referred to as Project
Management.
SDLC STAGE 9 & 10: Operation And Evaluation
Once a new system is operational evaluation of the system development process
begins.
Management: The process of getting activities completed efficiently and
effectively with and through people.
Efficiency: The relationship between inputs and outputs, seeks to minimize
resource costs.
Effectiveness: Goal attainment
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Evaluation provides the feedback necessary to assess the value of information and
the performance of personnel and technology included in the newly designed
system. This feedback serves two functions
It provides information as to what adjustments to the information system
may be necessary.
It provides information as to what adjustments should be made inapproaching future information systems development projects.
The operation evaluation is expected to answer the following questions-
1. Are all transaction processed on time?
2. Are all values completed accurately?
3. Is the system easy to work and understand?
4. Is terminal response time within acceptable limits?
5. Are reports processed on time?
6. Is there adequate storage capacity for data?
The post-development activities involves 1. Preparation of reports including the strength and weakness of the project.
(The report might review the need for recycling)
2. List reason for schedule and budget slippages.
3. Outline liaison and communications problems that occurred during the
system development
4. Identifying the mistakes, analyzing the reasons for the mistakes and how
they could have been avoided.
When the mistakes are identified they need corrections. Minor changes to the system
are called system maintenance, while major changes may initiate system
redevelopment
No
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Problem
Perceive
d
Planning
Feasibility Study
Acceptable
?
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Yes
Yes
No
Yes
No
No Yes
Introduction to Computer & MIS(Lecture Notes)
MHRDM/MFM/MMM-III
Prof. DG JHA
DocumentationDocumentation is the description of the system used to communicate, instruct and
record information for historical, operational or reference purposes. Documentation
establishes and declares the performance criteria of a system and provides
explanation of the system can be used. It should be designed in a format that is
easily understandable, so that relevant part of it can be used not only by the analysts
and technical personnels for implementation and modification, but also by users,
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Worth
Pursuing
?
Stop
Determine System
Requirement
Design System
Implement Design
Test System
OK?
Conversion
Control &
Operation
Evaluation
OK
?
Recycle to apt.
Point
Maintenance
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management, operational personnel and auditors for efficient operations and
administration.
Documentation has the production cycle of its own. Activities related to the
development and maintenance of documentation are:
No
Yes
Documentation must describe who, what, when, where, and how of each system (or
subsystem) application. Documentation can be produced in modules catering to the
specific use. This makes information easily accessible to the specific user for which
they are prepared, and reduce cost of production and maintenance.
The lists of manuals normally prepared are:
Users Manual
o For management
o For operations
Application System Manual
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State Ob ective
Plan & organize
with setting up of
standards
Pre are
Test
Approve &
Accept
Distribute
Use
Evaluate
Delay
OK
?
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Policy and Procedures Manual
Input Preparation Manual
Operations Manual
o For management
o For operator
Equipment Manualo For each equipment or device
Programmers Manual
Program Maintenance Manual
Special System Manual
o Operating System
o Control System
o Teleprocessing System
Standards Manual
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