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Information System (CS507)
LESSON 18
Systems Development Life Cycle
System Development Life Cycle (SDLC) is the overall process of developing information systems through a
multi-step process from investigation of initial requirements through analysis, design, implementation and
maintenance. SDLC is also known as information systems development or application development. SDLC
is a systems approach to problem solving and is made up of several phases, each comprised of multiple
steps. It describes the stages a system passes through from inception until it is discarded or replaced. SDLC
provides
1. Structure
2. Methods
3. Controls
4. Checklist
18.1 Project lifecycle vs. SDLC
The systems development life cycle is a project management technique that divides complex projects into
smaller, more easily managed segments or phases. Segmenting projects allows managers to verify the
successful completion of project phases before allocating resources to subsequent phases. Although System
development can be seen as a project in itself, but the attribute that makes system development different
from regular projects is that a project has a definite end and it is unlikely that ongoing maintenance will be
included in the scope of the project but this falls in the definition of SDLC.
18.2 Types of System Development Life-Cycle Model
The concept of system development lifecycle model has been explained in various shapes and forms. The
concluding form follows the same spirit except for minor differences.
Waterfall model / Classic lifecycle/ Linear Sequential Model
The waterfall model is a software development model (a process for the creation of software) in which
development is seen as flowing steadily downwards (like a waterfall) through the various phases
Incremental Models
In incremental models, software is built not written. Software is constructed step by step in the same way a
building is constructed. The products is designed, implemented, integrated and tested as a series of
incremental builds, where a build consists of code pieces from various modules interacting together to
provide a specific functional capability and testable as a whole.
Iterative Models
In these models customer feed back is taken at each phase and project is modified accordingly ­ if need be.
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Prototypes are used in these models.
Need Assessment
Information systems are usually developed on need-basis, that is, problems and opportunities arise and
render system development necessary. In this phase the stakeholders must attempt to come to some
understanding of the nature of the problem or opportunity they are addressing. Issues which can be
considered in this phase are. Is the problem
Well structured/Structured -- constrained problems with convergent solutions, limited number of rules
and principles within well-defined parameters.
Unstructured -- multiple solutions, fewer parameters, and contain uncertainty about which concepts and
rules.
Should formal terms of reference be prepared and approved by the steering committee or project
committee? This depends on the size, impact and cost of the system being prepared. The TOR usually
covers following aspects.
Investigation on existing system
Definition of system requirements
Specifying performance criteria for the system
Detailed cost budget
Draft plan for implementation
If the problem is decided to be addressed, the level of acceptance that exists among the stakeholders on the
need of change. The level of technological uncertainty the proposed solution to the problem/opportunity
has. The most critical phase is the agreement of the stakeholders on the definition of problem and
parameters of solution.
Entry and Feasibility Study
The purpose of this phase is to obtain a commitment to change and to evaluate whether cost effective
solutions are available to address the problem or opportunity that has been identified. Following examples
can be considered to explain this situation.
Say a problem has been recognized by a group of users. They believe they can design and implement a
solution themselves using a high level language. Their proposed system will have little impact on others
within the organization, nor will it be material from the viewpoint of the overall organization. In this
situation, the users are already motivated to bring about change. Thus activities to accomplish successful
entry are minor or unnecessary.
On the other hand, consider a solution where potential solutions will have a widespread impact on the
overall organization. Activities to accomplish successful entry are now critical. Information systems
professionals must seek to establish themselves as legitimate change agents among the stake holders.
Moreover they must seek to foster among the stakeholders a commitment to change. If potential
solutions will have a significant impact on task and social systems, a spirit of collaborative analysis and
evaluation among stakeholders must be developed.
Once the entry is successful, a preliminary study can be carried out to evaluate the feasibility of the new
system. A Feasibility study team should be constituted
Draw representatives from the departments affected by the project
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At least one person must have a detailed knowledge of computers and systems design (called system
analyst).
At least one person should have a detailed knowledge of
The organization
How current system operates
Information needs of the system
Defects in the existing system
Consultants from the outside
Key Areas of Feasibility
Following aspects/criteria can be covered in a feasibility study.
Technical Feasibility ­ is the available technology sufficient to support the proposed project? Can the
technology be acquired or developed?
Response times ­ time between request and execution
Volume of transactions which can processed within the given time
Capacity to hold files or records of a certain size
Number of users supported without execution
Operational Feasibility ­ compliance and adjustability with the way organization works with attitude to
change or chains of command.
Can the input data be collected for the system?
Is the output usable?
Economic feasibility ­ Do the benefits of the system exceed the costs?
It should be the BEST OPTION among those under consideration for the same purpose.
Behavioural feasibility ­ What impact will the system have on the user's quality of working life?
Reduction is job stress
Job satisfaction
Quality of output by employees
18.3 Costs of Proposed System
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18.4 Benefits from the proposed system
When a system is being introduced, management should consider the impact and amount of proposed
benefits. The purpose of this activity is to consider and
Better decision making
Savings
Possible in staff costs through increase of efficiency and not necessarily through redundancies.
In costs of running the department through more organized and efficient computerisation.
More sales revenue
Efficient use of staff time
Customer satisfaction
Better planning of resources required for operations e.g. inventory ordering, fixed asset utilization.
18.5 Classic lifecycle Model / Waterfall Model
Waterfall model is the earliest of software process models. Cascade of phases, the output of one is input to
the next. The waterfall model is a software development model (a process for the creation of software) in
which development is seen as flowing steadily downwards (like a waterfall) through the various phases.
Various phases of waterfall model are
Need Assessment
Entry and feasibility study
Analysis of the existing system
Information processing systems design ­ This also includes
Formulation of strategic requirements
Organizational & job design
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Program Development ­ this includes
Application software acquisition & development
Hardware/system software acquisition
Procedures development
Testing
Conversion
Operating & maintenance
Waterfall Model
Need
Assessment
Entry &
Feasibility
Study
System
Analysis
System
Design
Next
1
Waterfall Model
Previous
Program
Development
Procedures
Development
Testing
Changeover
Operations &
Maintenance
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Two phases need assessment and feasibility study, have already been explained in detail. Now let's take a
look at other phases one by one.
18.6 Analysis of Existing system
Once feasibility has been drawn up, next stage comes for analysis of existing system. Even if the existing
system is to be replaced the designers must study the existing system as this improves the quality of the
work. For example
The new system may change the way employees are rewarded. In such a case the redistribution of rewards
may have to be carefully negotiated. Concerns of employees cannot be ignored. Analysis is a two-part
episode. Studying organization's history, structure, culture ­ this would help to understand
The social & task systems
The way systems are coupled
Willingness of stakeholders to change (Change Management to be discussed later)
The greater the impact of the new system, greater time should be spent in understanding the present
organization. Analysis of existing product & information flows. This includes the use of various tools for
documenting the existing system. What these tools are will be discussed in detail in later Lessons.
System Design
System design includes the desired features and operations in detail, including screen layouts, business rules,
process diagrams other documentation. It involves converting the informational, functional, and network
requirements identified during the initiation and planning phases into unified design specifications. This
includes
Formulation of strategic requirements
Organizational & job design
Elicitation of detailed requirements
Design of the information flow
Design of database
Design of user interface
Physical design
Design of hardware & software platform
Formulation of Strategic Requirements
The overall goals and objectives the system must accomplish. Forms can be accomplished in any form, for
instance:
A vague goal ­ increase in the wealth of shareholders
A specific goal ­ reduce staff turnover by 30%
Strategic requirements for the new system are identified based on perceived deficiencies of existing system.
Trying to fit people and organizations into information systems has been major reason for failure. If
strategic requirements are clear, stakeholders are better placed to consider and evaluate alternative designs.
Organizational & Job Design
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Change in the strategic requirements will necessitate the change in the following for the parts of the
organization being affected
Organizational structure
Job descriptions for new or change in existing ones
Trying to fit people and organizations into information systems has been major reason for failure. So
change in both the above is important. If uncertainty surrounds the tasks to be accomplished in the
proposed system, loose organic organizational structures and job designs might be successful. Such promote
creativity and innovations. If organization is dominated by top management and culture is autocratic,
employees might be unwilling to accept the high level of responsibility.
18.7 Elicitation of Detailed Requirements
Designers must understand
What information an IS must provide
The data that must be captured to produce this information
Two approaches can be followed
Ask the stakeholders what they require ­ helps when they are clear about the requirements on
the basis of past experience or good understanding.
Analysis & experimentation ­ Where the ones bearing interest are not clear or have no past
experience, onus falls on the designer to work out the requirements.
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Table of Contents:
  1. Need for information, Sources of Information: Primary, Secondary, Tertiary Sources
  2. Data vs. Information, Information Quality Checklist
  3. Size of the Organization and Information Requirements
  4. Hierarchical organization, Organizational Structure, Culture of the Organization
  5. Elements of Environment: Legal, Economic, Social, Technological, Corporate social responsibility, Ethics
  6. Manual Vs Computerised Information Systems, Emerging Digital Firms
  7. Open-Loop System, Closed Loop System, Open Systems, Closed Systems, Level of Planning
  8. Components of a system, Types of Systems, Attributes of an IS/CBIS
  9. Infrastructure: Transaction Processing System, Management Information System
  10. Support Systems: Office Automation Systems, Decision Support Systems, Types of DSS
  11. Data Mart: Online Analytical Processing (OLAP), Types of Models Used in DSS
  12. Organizational Information Systems, Marketing Information Systems, Key CRM Tasks
  13. Manufacturing Information System, Inventory Sub System, Production Sub System, Quality Sub system
  14. Accounting & Financial Information Systems, Human Resource Information Systems
  15. Decision Making: Types of Problems, Type of Decisions
  16. Phases of decision-making: Intelligence Phase, Design Phase, Choice Phase, Implementation Phase
  17. Planning for System Development: Models Used for and Types of System Development Life-Cycle
  18. Project lifecycle vs. SDLC, Costs of Proposed System, Classic lifecycle Model
  19. Entity Relationship Diagram (ERD), Design of the information flow, data base, User Interface
  20. Incremental Model: Evaluation, Incremental vs. Iterative
  21. Spiral Model: Determine Objectives, Alternatives and Constraints, Prototyping
  22. System Analysis: Systems Analyst, System Design, Designing user interface
  23. System Analysis & Design Methods, Structured Analysis and Design, Flow Chart
  24. Symbols used for flow charts: Good Practices, Data Flow Diagram
  25. Rules for DFDs: Entity Relationship Diagram
  26. Symbols: Object-Orientation, Object Oriented Analysis
  27. Object Oriented Analysis and Design: Object, Classes, Inheritance, Encapsulation, Polymorphism
  28. Critical Success Factors (CSF): CSF vs. Key Performance Indicator, Centralized vs. Distributed Processing
  29. Security of Information System: Security Issues, Objective, Scope, Policy, Program
  30. Threat Identification: Types of Threats, Control Analysis, Impact analysis, Occurrence of threat
  31. Control Adjustment: cost effective Security, Roles & Responsibility, Report Preparation
  32. Physical vs. Logical access, Viruses, Sources of Transmissions, Technical controls
  33. Antivirus software: Scanners, Active monitors, Behavior blockers, Logical intrusion, Best Password practices, Firewall
  34. Types of Controls: Access Controls, Cryptography, Biometrics
  35. Audit trails and logs: Audit trails and types of errors, IS audit, Parameters of IS audit
  36. Risk Management: Phases, focal Point, System Characterization, Vulnerability Assessment
  37. Control Analysis: Likelihood Determination, Impact Analysis, Risk Determination, Results Documentation
  38. Risk Management: Business Continuity Planning, Components, Phases of BCP, Business Impact Analysis (BIA)
  39. Web Security: Passive attacks, Active Attacks, Methods to avoid internet attacks
  40. Internet Security Controls, Firewall Security SystemsIntrusion Detection Systems, Components of IDS, Digital Certificates
  41. Commerce vs. E-Business, Business to Consumer (B2C), Electronic Data Interchange (EDI), E-Government
  42. Supply Chain Management: Integrating systems, Methods, Using SCM Software
  43. Using ERP Software, Evolution of ERP, Business Objectives and IT
  44. ERP & E-commerce, ERP & CRM, ERP Ownership and sponsor ship
  45. Ethics in IS: Threats to Privacy, Electronic Surveillance, Data Profiling, TRIPS, Workplace Monitoring