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.
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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
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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
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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
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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
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