Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 1 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 Von Bertalanffy L. (1968) General Systems Theory: Foundations, Development, Applications, Penguin, London.

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 2 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

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 3 Types of systems (Checkland, 1981) Natural systems Designed physical systems Designed abstract systems Human activity systems INFORMATION SYSTEMS

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 4 Types of model Predictive models Normative or optimising models Descriptive models

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 5 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.

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 6 Types of activities and information MANAGEMENT ACTIVITIES FUNCTIONAL ACTIVITIES

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 7 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)

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 8 Process InputOutput FUNCTIONAL SYSTEM SensorStandard Control device Activating unit CONTROL SYSTEM E E

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 9 FUNCTIONAL SYSTEM CONTROL SYSTEM Design

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 10 FUNCTIONAL SYSTEM CONTROL SYSTEM Information system Management system Information Changes Applying the systems approach

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 11 FUNCTIONAL SYSTEM CONTROL SYSTEM Information base Management system Information Changes Simulation system Message system Input system Output system HCS Information system Event

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 12 Interaction of functional and control systems 1. The event occurs in the functional system 2. The human computer system (input system) records details concerned with the functional system event 3. The input system initiates appropriate simulation system process 4. The simulation system process updates the information base 5. 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

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 13 Management system components Information system Internal usersExternal users InformationalDecision makingInterpersonal Management system

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 14 Applying the systems approach OMNIS model an Overview Model of aN Information System in its organisational context Functional system Static component Dynamic component Input/output ObjectProperty RuleBehaviour EventProcess

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 15 OMNIS model Control system Information system Management system Simulation system Message system Human computer system Information base Rule base Process RuleObjectProperty Event Input system Output system Data capture Transact. input QueryReport

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 16 OMNIS model ORGANISATION Control system Information system Management system Simulation system Message system Human computer system Information base Rule base Process RuleObjectProperty Input system Output system Event Functional system Static component Dynamic component Input/output ObjectProperty RuleBehaviour EventProcess Data capture Transact. input QueryReport

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 17 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

Flynn, D.J. Information Systems Requirements: Determination and Analysis, McGraw-Hill International (UK) Limited,1992 Marite Kirikova, RTU 18 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