1. Introduction to Systems CSCI102 - Systems ITCS905 - Systems MCS9102 - Systems

2. 2 Definitions - System An organized or connected group of objects –A set or assemblage of things connected, associated, or interdependent, so as to form a complex unity –A whole composed of parts in orderly arrangement according to some scheme or plan –Rarely applied to a simple or small assemblage of things Of artificial objects or appliances arranged or organized for some special purpose, as pulleys or other pieces of mechanism, columns or other details of architecture, canals, railway lines, telegraphs, etc

3. 3 Definitions - System Linguistics. A group of terms, units, or categories, in a paradigmatic relationship to one another Computers. A group of related programs; spec. = operating system

4. 4 Definitions - System With reference to business and social organizations and the operations or interactions they involve The set of correlated principles, ideas, or statements belonging to some department of knowledge or belief –A department of knowledge or belief considered as an organized whole –A connected and regularly arranged scheme of the whole of some subject –A comprehensive body of doctrines, conclusions, speculations, or theses

5. 5 Definitions - System A formal, definite, or established scheme or method –Classification –Notation etc Special Combination –As systems (or system) analysis, the rigorous, often mathematical, analysis of complex situations and processes as an aid to decision-making or preparatory to the introduction of a computer

6. 6 Types of Systems - Information System? An information system differs from other kinds of systems in that its objective is to monitor/document the operations of some other system, which we can call a target system An information system can not exist without such a target system –Production activities would be the target system for a production scheduling system –Human resources in the business operations would be the target system of a human resource information system

7. 7 Types of Systems - Information System? For example: within a vending machine there is a component/sub-system that can be considered an information system In some sense, every reactive system will have a subsystem that can be considered an information system whose objective is to monitor and control such a reactive system

8. 8 Types of Systems – System Analysis? What is System Analysis? –A Formal Definition: Systems analysis is the dissection of a system into its component pieces for purposes of studying how those component pieces interact and work –Systems analysis is done for the purpose of subsequently performing a systems synthesis Systems synthesis is the re-assembly of a system’s component pieces back into a whole system – hopefully an improved system

9. 9 A Contextual view Any system operates by interacting with its environment –The contextual view describes graphically the interaction of the system with the various entities in its environment –The interactions consist of dataflows from and to such entities –The contextual view clarifies the boundary of the system and its interfaces with the environment in which it operates Contextual views can be realised by methods such as mind mapping

10. 10 A Control view Any system must manipulate certain variables in order to achieve its objectives It determines the manipulation needed by processing its outputs/states in relation to certain control parameters.

11. 11 Some basic concepts & strategies in the study of systems Abstraction: –``We have developed an exceptionally powerful technique for dealing with complexity. We abstract from it. Unable to master the entirety of a complex object, we choose to ignore the inessential details, dealing instead with the generalized, idealized model of the object" Wulf in Shaw, 1981 Formality: – Rigor at each stage in the development of a system

12. 12 Some basic concepts & strategies in the study of systems Divide and conquer: –Divide a complex problem into a set of simpler problems that can be solved Hierarchical ordering: –Order the simplification of the problem in ``divide & conquer" in hierarchies Cohesion & coupling: –Modularise the system such that interactions within components (cohesion) is maximised and interactions between components (coupling) is minimised –This way, the impact of errors, when they arise, is localised and does not cascade through the system –Diagnosis of offending components is also made easier

13. 13 Some basic concepts & strategies in the study of systems Information hiding: –Each module (or subsystem) must have available to it just the information that is needed by it Conceptual integrity: –Consistency in design

14. 14 Some basic concepts & strategies in the study of systems Completeness: –Ensuring that the design meets all the specifications Logical independence: –Emphasis on the statement of system objectives in terms of logical functions independent of physical implementation Correctness & Efficiency: –Correct in the sense that the design meets all the user requirements –Efficient in that the system accomplishes the objectives with minimum computing resources