Systems Terminology:

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Systems Terminology

• Environment
• Systems do not operate in complete isolation.
  They are contained within an environment that
  contains other systems/external agencies.
• Systems Boundary
• This describes the interface between a system and
  its environment. Everything within the boundary
  forms part of the system, everything outside the
  boundary forms part of the external environment.
• Interface
• In terms of systems, the interface describes the
  exchanges between a system and its environment or
  the system and other systems.

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• Open Systems
• Interaction occurs with elements beyond the
  system boundary
• Closed System
• No or limited interaction occurs with the
  environment
• Subsystem
• A group of related activities which are part of
  an overall system. Each subsystem has clearly
  defined inputs and outputs. Most business systems
  can be divided into subsystems
• Synergy
• Synergy means that the whole is greater than the
  sum of the parts

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• Hierarchical Systems
• Systems are hierarchical in nature, being made up
  of subsystems that may themselves be made up of
  other subsystems
• Interdependence
• Interdependence means that a change to one part
  of a system leads to or results from changes to
  one or more other parts

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System Environment
Control Mechanism
Management
Information System
Input
Process
Output
Information Systems as an organisational control
mechanism
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• The role of the IS is to provide information to
  management which will enable them to make
  decisions which ensure that the organisation is
  controlled. The organisation will be in control
  if it is meeting the needs of the environment.
  The elements of the environment which are
  relevant to an organisation are termed its
  stakeholders. These include customers,
  competitors and suppliers.
• One of the characteristics of a system is that
  its behaviour is directed towards some objective
  or goal. It does this by means of a control
  mechanism, which is termed either open loop or
  closed loop.

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Open-loop control system An open-loop control
system is one in which there is an attempt to
reach the system objective, but no control action
to modify the inputs or process is taken once the
process has begun.
System Environment
Input
Process
Output
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Closed-loop control systems Two types of control
mechanism that can be employed in this situation
are Feedback Control and Feedforward
Control 1) Feedback Control - The output
achieved is monitored and compared to the desired
output and corrective action is taken if a
deviation exists. The mechanism emphasizes the
fact that in order to control any system such as
a business system, information about its current
output state is needed in order that appropriate
action can be taken to adjust inputs. If this
link between output an input is broken, the
process will not be controlled.
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System Environment
Control Mechanism
Input
Process
Output
A generic closed-loop feedback control system
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• Positive and Negative Feedback
• The term negative feedback is used to describe
  the act of reversing any discrepancy between
  desired and actual output. Thus in a business
  setting a budget overspend would be responded to
  by actions leading to a reduction in this
  variance.
• The term positive feedback responds to a
  variance between desired and actual output by
  increasing that variance. A business example is
  rapid sales growth increasing production levels
  leading to increased sales.

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2) Feedforward control Feedforward control
systems attempt to overcome the over-correction
and time delay disadvantages of feedback systems
by incorporating a prediction element in the
control feedback loop. Good examples - stock
control (Xmas)
System Environment
Control Mechanism
Input
Process
Output
A generic closed-loop feedforward control system