1

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

The systems approach

• Churchman, C.W. (1968) The Systems Approach, Dell Publishing Co., New York.

• Ackoff, R.L. (1971) Towards a system of system concepts. Management Science, Vol. 17, No. 11, P. 661-671.

• Von Bertalanffy L. (1968) General Systems Theory: Foundations, Development, Applications, Penguin, London.

2

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

Definition of the system

• A system is an assembly of parts or components existing together in an organised way

• The assembly is of particular human interest

• Parts are affected by being in the system - they change if they leave

• The assembly does something - it has an aim

Open University definition

3

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

Types of systems (Checkland, 1981)

•Natural systems•Designed physical systems•Designed abstract systems•Human activity systems

INFORMATION SYSTEMS

4

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

Types of model

• Predictive models• Normative or optimising models

•Descriptive models

5

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

The systems approach

Main concepts and assumptions

• basic concepts– described in terms of input, output, process, boundary,

environment

– input and output - static objects transformed by dynamic processes

• control system is essential for unpredictable systems

• The state space approach - views processes (update processes) as transformations between one state to another. A state at a given instant consists of the objects in the system at that instant.

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

Types of activities and information

MANAGEMENTACTIVITIES

FUNCTIONAL ACTIVITIESFUNCTIONAL ACTIVITIES

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

• functional activities– processing a shipment order

– paying employee wages

– processing sales

– ...

• management activities– scheduling jobs

– hiring and firing staff

– managing departmental budgets

– checking organisational performance against objectives

– deciding on new markets or strategies

– ...

Types of activities and information(EXAMPLES)

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

ProcessInput Output

FUNCTIONAL SYSTEM

SensorStandard

Controldevice

Activatingunit

CONTROL SYSTEM

E E

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

FUNCTIONAL SYSTEM

CONTROL SYSTEM

Design

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

FUNCTIONAL SYSTEM

CONTROL SYSTEM

Informationsystem

Management system

Information

Information

Changes

Applying the systems approach

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

FUNCTIONAL SYSTEM

CONTROL SYSTEM

Informationbase

Management system

Information

Information

Changes

Simulationsystem

Messagesystem

Input system

Output system

HCS

Informationsystem

Event

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

Interaction of functional and control systems

1. The event occurs in the functional system2. The human computer system (input system) records

details concerned with the functional system event3. The input system initiates appropriate simulation

system process4. The simulation system process updates the

information base5. The user initiates the human computer system

(output system) process to start the appropriate message system process to obtain information from information base

6. The user performs the management system activity using the information obtained

7. Possible changes are made to the functional system

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

Management system components

Information system

Internal users External users

Informational Decision making Interpersonal

Management system

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

Applying the systems approach

OMNIS modelan Overview Model of aN Information System in

its organisational context

Functional system

Staticcomponent

Dynamiccomponent

Input/output

Object Property

Rule Behaviour

Event Process

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

OMNIS model

Control system

Informationsystem

Management system

Simulationsystem

Messagesystem

Human computersystem

Informationbase

Rulebase

Process

Rule Object Property

Event

Inputsystem

Outputsystem

Data capture

Transact.input Query Report

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

OMNIS modelORGANISATION

Control system

Informationsystem

Management system

Simulationsystem

Messagesystem

Human computersystem

Informationbase

Rulebase

Process

Rule Object Property

Inputsystem

Outputsystem

Event

Functional system

Staticcomponent

Dynamiccomponent

Input/output

Object Property

Rule Behaviour

Event Process

Data capture

Transact.input

Query Report

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

OMNIS Principles

•Non-redundancy - model fact only once

•Completeness - model all the relevant facts

•Accuracy - do not invent facts (model only what is in the description)

•Clarity– model fact as an object rather than a property

– only model important properties

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Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992

Marite Kirikova, RTU

The systems approach

Advantages and disadvantages

• Advantages– description of system using intuitively familiar notions

(input, output, process)

– decomposition

– notion of control system

– description suitable for communication

• Disadvantages– possibility of non-unique descriptions

– there is no guidance concerning level of detail (possibility of incompleteness of description)

– no method is suggested to apply approach