1. Concepts of Systems Theory

2. 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?

3. 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

4. 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.

5. Characteristics of a System

6. 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

7. 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?

8. 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

9. 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?

10. 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

11. 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.