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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