Systems Theory

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Systems Theory

• CBIS Lecture 2

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Definitions of Systems

• An organised or complex whole, or
• Organised complexity, or
• An entity which consists of interdependent parts.
• A collection of people, machines and methods
  organised to accomplish a set of specific
  functions

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The Communications Model
Destination
Your boss has an idea
Writes a memo
Internal mail
You read memo
You understand The idea
You write an e-mail message
Computer network
Boss reads the e-mail
You have an idea
Boss understands The idea
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Component Parts of a System

• Inputs provide the system with what it needs to
  operate
• Processes a process transforms an input into an
  output
• Outputs these are the results of the operation
  of the system
• System boundary defines the areas or
  constraints in which the system operates
• Environment anything which is external to the
  system
• System communications although systems are
  separated from their environments, they need to
  communicate with it
• Noise faults which result in a partial or total
  breakdown in communication,,, not getting the
  message across

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Types of Systems

• Closed System one which is completely isolated
  from its environment and neither influences or is
  influenced by it

Shut off from Its environment

• Open System fully interacts with its
  environment. All business organisations are open
  systems.

Relating to its environment in both prescribed
and uncontrolled ways
Controllable Inputs
Predictable Outputs
Uncontrollable Inputs
Unpredictable Outputs
Unexpected Inputs
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System Adaptability

• A system must be able to react to changes in the
  environment if it is to survive it does this in
  3 ways

• Deterministic systems behave in completely
  predictable ways

Predictable Input
Predictable Output
System reacts in predictable way
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System Adaptability

• Probabilistic systems here inputs are
  unpredictable and systems must adapt accordingly

Input Probability
System reacts according to the nature of the input
Type A 0.3
Type B 0.4
Output depends on the nature of the input
Type C 0.2
Type D 0.1
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System Adaptability

• Self organising systems here system responses
  are unpredictable.

Output depends on whether and how the system has
adapted
System adapts to the changing nature of inputs
Input might vary or change over time
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Systems Approach and Organisations

• Highlight the dynamic aspects of business
  organisations
• Create an awareness of subsystems, each with
  conflicting goals
• Assist in the design of information systems
• Help identify the effect of the environment on
  internal systems

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Hierarchy of Systems

• A system is composed of subsystems
• Given any system, it is always possible to find
  another system of which that system is a part
• Given the systems, the greater is called the high
  level system, the smaller is the low level system
• A hierarchy of systems exists whereby high level
  systems are comprised of low level systems
• Low level systems are in turn made up of other
  systems for which they are considered as high
  level systems

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Control and Feedback

• A system must be controlled to keep it stable or
  enable it to change safely.
• Control is necessary because unpredictable
  disturbances arise and enter the system,
  resulting in the actual performance deviating
  from some desired value.

TWO TYPES OF CONTROL

• Open Loop Systems
• Closed Loop Systems

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Open Loop System

• Is one where the control action is triggered by
  external sources. Open Loop systems are more
  common at Strategic rather than at Tactical or
  Operational levels.

An example here would be a company comparing some
aspect of its activities with another and making
a series of changes to its activities in response.
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Closed Loop System

• Is one where part of the output is feedback, so
  that the output can initiate control action to
  change either the activities of the system or the
  systems inputs.

A good example here would be a budgetary control
system.
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The Closed Loop
Input
Process
Output
Actual Performance
Comparison of Actual and Planned Performance
Corrective Action
Planned Performance
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Positive Feedback

• Positive feedback results in a control action
  which causes actual results to maintain (or
  increase) from the planned course.

August Sales
July Sales
June Sales
Planned Sales 100,000
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Negative Feedback

• Negative feedback results in a control action
  which seeks to reverse the direction or movement
  of the system back towards its planned course.

July Sales (need to be higher)
Planned Sales 100,000
June Sales
Actual 90,000
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The Control Model
Input
Process
Output
Detector
Comparator
Effector
Standard