System Development Notes
System Fundamentals and Classification
A system is a set of items linked together to perform a given task and achieve one or more objectives. Systems are described as either soft systems or hard systems. Soft systems represent human activities characterized by fluid boundaries, conflicting goals, and performance metrics that are difficult to define. Hard systems possess clearly defined goals, predictable outcomes, and processes that can be accurately modeled.
Systems are classified based on output predictability and environmental interaction into deterministic, probabilistic, cybernetic, open, and closed systems. A deterministic system provides outputs precisely known from its inputs, whereas a probabilistic system's outputs can only be predicted. Cybernetic systems are self-controlling systems that regulate behavior and adapt to their environment using feedback. Open systems exchange inputs and outputs with their environment, while closed systems do not interact with the environment.
System Characteristics and Control
Systems possess distinct characteristics including holistic thinking, subsystems, processors, objectives or purpose, environment, boundaries, interdependence, feedback, control, inputs and outputs, and system entropy. Holistic thinking treats the system as a complex whole whose overall goals surpass those of individual components, while subsystems form its constituent parts. A processor transforms input into output, and system entropy represents natural system decay over time due to technological advances, management changes, or evolving user requirements.
System control enables a system to adapt to environmental changes to maintain expected performance levels. Inputs and outputs serve as communication mechanisms with the external environment, while feedback evaluates whether predetermined goals are met and identifies operational deviations.
Information Systems Overview
An information system is a set of persons, procedures, technologies, and resources that collects, transforms, and disseminates information within an organization. Its primary purpose is to assist in organizational decision-making, provide responsive service to meet user needs, enable information sharing, and facilitate data dissemination across all organizational levels.
Organizations undertake the development of a new information system due to management changes, operational problems in the current system, or new opportunities to enhance service delivery.
System Development Approaches
System development theories include the Traditional Approach, Rapid Application Development (RAD), and the Structured Approach. The Traditional Approach relies on individual staff experience and computerizes manual systems without changing their overall structure, carrying former weaknesses forward into the new system. Rapid Application Development (RAD) focuses on quick development and implementation to preserve competitive advantage in technology-reliant markets.
The Structured Approach defines a formal sequence of stages to follow during system development, known as the system development life cycle.
System Development Life Cycle Stages
The structured development life cycle consists of seven main stages: problem recognition and definition, information gathering, requirements specification, system design, system construction, system implementation and testing, and system review and maintenance. Problem recognition involves defining the issue and conducting a feasibility study covering operational feasibility, technical feasibility, economic feasibility, and schedule feasibility. Information gathering collects data via record inspection, interviews, questionnaires, observation, or automated capture devices.
Requirements specification details output formats, input parameters, data stores, and hardware/software needs. System design outlines physical specifications and operating procedures using design tools such as flowcharts and data flow diagrams. System construction involves coding and module integration. Implementation encompasses file creation and conversion, staff training, and system changeover using direct changeover, parallel changeover, or phase changeover methods. Post-implementation review and maintenance adjust and enhance the system to ensure it meets original specifications.
Questions & Discussion
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