Concepts of Systems Theory

Contemplative Questions What is systems thinking? Why do ‘systems thinkers’ get promoted? How does the field of information systems benefit from concepts of systems theory? How can we use these concepts in the real world?

Systems Thinking System A system is an interrelated set of business procedures used within one business unit working together for a purpose A system has nine characteristics A system exists within an environment A boundary separates a system from its environment 2.3

Characteristics of a System Components Interrelated Components Boundary Purpose Environment Interfaces Input Output Constraints On a sheet of paper, define each of these terms in your own words.

Characteristics of a System

Systems Thinking Important System Concepts Decomposition The process of breaking down a system into smaller components Allows the systems analyst to: Break a system into small, manageable subsystems Focus on one area at a time Concentrate on component pertinent to one group of users Build different components at independent times

Systems Thinking Important System Concepts Modularity Process of dividing a system into modules of a relatively uniform size Modules simplify system design Coupling Subsystems that are dependent upon each other are coupled Cohesion Extent to which a subsystem performs a single function Which is better: More or less modularity? High or low coupling? High or low cohesion? Suppose you work as a systems analyst in a large organization. Your boss comes into your office and gives you a project requiring changes to another department’s system. Would you rather the existing systems have high or low coupling? high or low cohesion? more or less modularity?

Systems Thinking Important System Concepts Logical vs. Physical Modeling Logical System Description Portrays the purpose and function of the system Does not tie the description to a specific physical implementation Physical System Description Focuses on how the system will be materially constructed

Systems Thinking Benefits Identification of a system leads to abstraction From abstraction you can think about essential characteristics of specific system Abstraction allows analyst to gain insights into specific system, to question assumptions, provide documentation and manipulate the system without disrupting the real situation Example. Identify a system used by the university. Use the characteristics of systems in general to describe your system. What insight can you gain from this exercise?

Systems Thinking Applying Systems Thinking to Information Systems Information systems are subsystems in larger organizational systems Data flow diagrams represent information systems as systems Inputs Outputs System boundaries Environment Subsystems Interrelationships 2.10

Decomposition Example Figures 8-4 and 8-5. What system characteristics are demonstrated in these pictures? What do the diagrams tell you? Which diagram is more useful? Show decomposition of the system, balancing between diagrams, inputs, outputs, boundary, components, etc. Context diagram in top left shows the context of the system within its environment. It is purposely simple. Right hand side shows more detail of Food Ordering System. Each is useful in its own right. Context shows a quick summary. Level 0 on the right is more detailed. This is the beauty of decomposition—more information conveniently represented.