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8/8/2019 37210353 System Concepts
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System Concepts:System Concepts:
y Definition of a System; General Model Of
A System; Types Of Systems, Subsystems,
Organizational Efficiency And
Effectiveness
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y Introduction
The term system is a commonly used word. One
speaks of an educational system, computer system,system of theology, and many others.
An information system is, as its name implies, a special
type ofsystem. System theory (or concept) provides a
useful framework for describing and understanding
many organizational phenomena including features of
information systems and how they may be analyzed and
designed
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y Definition ofa System.
Since a system is a subjective concept, there is no
unanimously accepted definition of a system. In order tostudy this phenomenon more closely, we will adopt thefollowing definition:
A systemis an organised assembly ofcomponents withspecial relationships between the components.
The system does something, i.e. it exhibits a type ofbehaviourunique to the system or has a specific objectiveor purpose.
Each component contributes specifically towards the
behaviour of the system and is affected by being in thesystem. If a component is removed, it will change thesystem behaviour.
Someone has identified the system as being of specialinterest.
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y An information systemis a system that gathers
and transforms data in order to produce
information for its end-users. If it is to functionsuccessfully, then its developers and its users must
agree on the purpose of the system, its
components and the relationships between them.
y Another essential element of the definition
involves the subjective aspect: a system is not anobjective thing out there that exists on its own
but it is something attributed to a set of
interrelated components by an observer.
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y The Systems View and SystemsThinking
The definition of a system is, however, somewhat of an
academic exercise. The real essence of systems theory
is being able to look at the world from a different
perspective.
The systems viewinvolves adopting the reference
framework and the terminology of systems theory,
trying to apply various analogies with other systemsand checking which of the systems laws and theories
hold for the system of interest.
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yWhy is this systems view so important?
y Can we not just learn about the technology of
information systems and dispense with more
philosophical matters?
y The problem with the purely technical approach is
that it often fails to take into account the inter-
relation of problems and proposed solutions,which is incorporated in the systems view
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y General Model OfA System
y A general model of a physical system is input, process,
and output as illustrated next.
y Environment and Boundary
y As soon as we identify a system, we define aboundary: what is inside the boundary belongs tothe system, everything outside the boundary is notpart of the system. However, most systems do notexist in isolation. Systems, or their components, inter-act with the world outside their boundary. The partof the outside world with which the system interactsis called the systems environment
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Transformation
Process
System Environment
Input Output
Feedback
System Boundaryinterface
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y Components and Subsystems
y A system consists of various components which,
taken together, make up the system. (Subsystems)y Each system is thus composed of subsystems
which in turn are made up of other subsystems,each subsystem being delineated by itsboundaries.
y The interconnections and interactions betweenthe subsystems are termed interfaces. Interfaces
occur at the boundary and take the form of inputsand outputs. See text
y The level of detail with which you study a givensystem is called the granularity
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y The coarsest possible description of a system is
called the blackbox view of the system:
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y Objectives,Control and Feedback Loops
Systems have a function, goal or purpose. This goal
can be internalised e.g. the desired room temperaturefor a central heating thermostat device or the profit
motive in a commercial business enterprise.
This purpose can also be imposed from the outside e.g.
when we use a motor car to drive from our home to
the shop.
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In order for the system to achieve its goal(s), it needs
to be able to modify its behaviour.
Control is the mechanism whereby the system is able
to modify the processes and activities (behaviour).
Controls which occur within the system are referred
to as control signals and
Controls which come from outside the system arereferred to as control inputs.
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y This round trip of using output signals and using
them to modify input signals is called a feedback
loop, and the whole process is one offeedbackcontrol.
y There is always a slight delay before the outputcan be interpreted, the consequent control
changes are effected and the system behaviour is
adjusted. This delay is called the (time) lag.
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y System feedback can be positiveor negative. If
the system behaviour needs to be altered
(reversed) in order for its output to move closerto the desired state, then we have a negative
feedback loop.
y However, if the feedback loop reinforces thecurrent behaviour of the system, then we speak of
positive feedback
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y Types OfSystems
Deterministic and Probabilistic Systems
A deterministic system operates in a predictable
manner. The interaction among the parts is known with
certainty. If one has a description of the state of the
system at a given point in time plus a description of its
operation, the next stage of the system may be given
exactly without error.
The probabilistic system can be described in terms of
probable behaviour, but a certain degree of error isalways attached to the prediction of what the system
will do
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y Closed and Open Systems
y A closed system is defined in physics as a system
which is self-contained. It does not exchangematerial, information or energy with itsenvironment. An example is a chemical reactionin a sealed, insulated container. Such closed
systems will finally run down or becomedisorganized. This movement to disorder istermed an increase in entropy
y
In organizations and in information processing,there are systems that are relatively isolated fromthe environment but not completely closed in thephysics sense. These will be called closed systems,
meaning relatively closed.
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y Dynamic vs Static Systems
A dynamic systemis a system that has at least one
(and usually many) activity or process; as opposed to astatic system, which has no activity, whatsoever
y
Continuous vs Discrete Systems A continuous systemis a system where inputs (and
outputs) can be varied by extremely small amounts or
quantities.Discrete systems are systems where the
inputs or outputs can take on only certain discrete ordistinct values.
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y Structure and Hierarchy
The interactions between the various sub-systems and
components of a system display some pattern orregularity. In this sense the observer can identify
certain relationships, which contribute to the overall
behaviour of the system. The entire set of relationships
is referred to as the structureof the system.
Smaller sub-systems are thus embedded within the
system, which in turn may be a sub-system of yet
another, larger system: the supra-system. This nesting
of systems within systems within systems is referred to
as a systemhierarchy
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y Holism and Emergent Properties
The perspective from which claims that many aspects
of a system can be understood only in terms of itsentirety, and not necessarily be reduced to the
characteristics of its components, is called holism(the
opposite ofreductionism).
This is often expressed in the popular saying that a
system is more than the sum ofits parts.
Holism also implies that it is important to be aware of
the inter-relation between the various components of a
system.
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y The holistic systems view implies that a system
has certain properties, qualities or attributes
which cannot be reduced to or understood fromits components alone. These properties are called
the emergent properties of a system.
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y Entropy
An important measure of a system is the amount of
order (in the case of matter or information) orpotential energy it contains. The measure for disorder
or energy degradation is entropy: the higher the level
of disorder, the higher the entropy level. All systems
change over time and, unless a system can draw onresources from the environment, it will tend to
become more disorderly or lose energy (run down)
i.e. entropy increases.
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y Decomposition
y A complex system is difficult to comprehend
when considered as a whole. Therefore, thesystem is decomposed or factored intosubsystems
y The subsystems resulting from this processgenerally form hierarchical structures. In thehierarchy, a subsystem is one element of asuprasystem (the system above it).
y
The general principle in decomposition whichassumes that system objectives dictate theprocess is functionalcohesion. Components areconsidered to be part of the same subsystem if
they perform or are related to the same function
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y Organizational Efficiency And Effectiveness
Systems concepts suggest two major classes of
performance measurement:Effectiveness andEfficiency.
y Effe
ctive
ness is a measure of actual output againstdesired output. It represents the reason the
system exists. It is a measure of the extent to
which a system achieves its goals and can be
computed by dividing the goals actually achievedby the total of the stated goals
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y Efficiencyis a measure of the relative cost of
producing output. It is the use of inputs to
produce output. It is a measure of what isproduced divided by what is consumed.
y Organizations tend to measure and controlefficiency more than effectiveness.
y The reason is that efficiency measurements tend
to be easier to obtain and more precise informulation often leading to the production of
wrong output efficiently.
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y Information system development for applications
may be measured by adherence to budget and
development standards (efficiency) with noattention to how well the application meets the
needs of the customers (effectiveness).
y A word processing centre monitors keystrokes,
errors, and lines produced (efficiency) but not
whether the documents produced have higher
quality than typewritten documents
(effectiveness).
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