Information Systems Development Life Cycle Explained

Posted on Jan 28, 2025 in Software Engineering

Information System (IS): A system that assembles, stores, processes, and delivers information relevant to an organization in such a way that the information is accessible and useful to those who wish to use it.

IS Development: The way in which information systems are conceived, analyzed, designed, and implemented.

IS Development Methodology: A collection of procedures, techniques, tools, and documentation aids that will help the systems developers in their efforts to implement a new information system.

Need for a Methodology

Early applications of computers were implemented without the aid of an explicit information systems development methodology. As a result:

  • The needs of users were not well established.
  • IS was inappropriate for the application.
  • Few programmers would follow any formal methodology.

This led to several issues:

  1. Estimating the operational date was difficult.
  2. Programmers were overworked.
  3. Time was spent correcting errors.
  4. Time was spent enhancing applications that were already operational.

Information Systems Development Life Cycle (SDLC)

Basic Structure:

  1. Feasibility Study
  2. System Investigation
  3. Systems Analysis
  4. Systems Design
  5. Implementation
  6. Review and Maintenance

Feasibility Study

Presents:

  1. System
  2. Requirements that were intended to be met
  3. Problems in meeting requirements
  4. New requirements that have come to light since implementation
  5. Alternative boundaries of the system and constraints

Must be feasible in these four areas:

  • Legally
  • Organizationally and Socially
  • Technically
  • Economically

System Investigation

(Fact-finding phase) – Looks at:

  1. Functional requirements of the existing system
  2. Requirements of the new system
  3. Constraints imposed
  4. Range of data types and volumes to be processed
  5. Exception conditions
  6. Problems of present working methods

Fact-finding methods:

  1. Observation
  2. Interviewing
  3. Questionnaires
  4. Searching records and documentation
  5. Sampling

System Analysis

Asks questions such as:

  1. Why do problems exist?
  2. Why were certain methods of work adopted?
  3. Are there alternative methods?
  4. What are the likely growth rates of data?

Provides pointers to the new design and ascertains the requirements of the new system.

System Design

Design of both the computer and manual parts of the system.

Implementation

  1. Write and test computer programs
  2. Purchase and install new hardware and software
  3. Quality control: manual procedures, hardware, and software are to be tested to the satisfaction of the user
  4. Education and training of user staff
  5. Produce documentation, such as operations and user manuals
  6. Test security procedures
  7. Operate the system

Review and Maintenance

Final Stage: Ensures that the system conforms to the requirements set out at the feasibility study stage and that the cost does not exceed what was predicted. This leads to improvements in the way other systems are developed, fostering organizational learning.

Weaknesses of SDLC

  1. Failure to meet the needs of management
  2. Instability
  3. Inflexibility
  4. User dissatisfaction
  5. Problems with documentation
  6. Lack of control
  7. Incomplete systems
  8. Application backlog
  9. Maintenance workload
  10. Problems with the ‘ideal’ approach
  11. Emphasis on ‘hard’ thinking
  12. Assumption of ‘green-field’ development