IMS1805 Systems Analysis

1. IMS1805Systems Analysis Topic 2: Introduction to some key techniques for systems analysis in IS

2. Recap of last lecture • Information systems comprise a mixture of many different types of components – people, things, actions, etc • Analysis involves deciding which of these elements will be selected for inclusion as part of the explanation/representation of the system • Different techniques are used, depending on which system elements you wish to focus on in your analysis

3. Agenda • Aim: To demonstrate some of the diagrammatic techniques commonly used in IS analysis • To note what elements of a systems are highlighted by each technique • To begin to develop some idea of why each might be useful • (Note: Ground level at last!)

4. 2. Evolving role of analysis in IS • Stages (eras) in the development and use of technology; (note, these eras are cumulative, not substitutes for one another) • Circularity of technology drives usage drives technology drives usage and so on ….. • Development of analytical tools to complement technological capabilities and usage • All these analytical tools have some general principles in common

5. (a) Logic-based analysis – task sequence and flowcharting • Derived from use of computers as calculating machines for specific individual tasks • Closely linked to computer programme structures - algorithms • Main analytical tools are programming-oriented (flowcharts, etc) • Aim of analysis is to show sequence of actions and flow of logic • Key elements: • Actions • Connection - sequence • Data/information inputs and outputs

6. Flowchart example Student inserts card Student ID BIS Students Look for student ID In BIS student file Display red light Is student ID valid? No Yes Show green light and unlock door End

7. (b) Process-based analysis – (i) analysis of hierarchy of processes • Aim to simplify by focussing solely on processes • Focus of analysis is on: • the processes done by the system • the hierarchical structure of those processes • This form of analysis fits well with the classic hierarchical organisational chart – organisational units vs business functions • Key elements: • Actions (processes) • Connections (process parent-child relationships)

8. Functional decomposition diagram (hierarchy chart) example

9. Process-based analysis – (ii) analysis of movement of data between processes (DFDs) • IS are used to transform data and information; therefore focus on the processes which do the transforming and the data/information which are input to and output from each process • The heart of the method called structured analysis • Key elements: • Actions (processes) • Stores of data • Related systems, people, things • Connection (flow of data)

10. BIS Students Data Flow Diagram (DFD) example Read student details Identification details Student ID Valid student IDs Validate Student ID Authorisation

11. (c) Data-oriented analysis - analysis of data structures for database technology • Based on a view that processes may often change within an organisation, but the data/information needs will not; therefore data/information gives a more stable picture • Associated with the growth of packaged database management software • The heart of Information Engineering methods • Key elements: • Things about which data is stored • Connections between these things (data/attributes in common)

12. Entity-relationship diagram example Student Course Enrols in comprises Unit Unit leader runs

13. (d) Object-oriented analysis • O-O programming languages originated in 1960s; achieved widespread from the 1990s • Based around use of programming ‘objects’ with both data and process elements (contrast with languages which separate data from process) • A range of analytical techniques have followed: • Activity diagrams; class diagrams, communication diagrams; use case diagrams, interaction diagrams, etc • Key elements: • Things and people (called classes and objects) • Processes (called methods and behaviours) • Events (called messages)

14. Use case diagram example of an object-oriented (O-O) analysis technique Timetable unit Enrol in unit Lecturer Enrol in tutorials Timetable exam Student Submit results Admin officer Publish results

15. (e) “Soft systems” analysis • Grew out of concern that existing analytical methods omitted key ‘people’ elements of systems - motivations/attitudes/feelings • Range of techniques developed to highlight some of these aspects of system • Much vaguer, less structured techniques • Examples - rich pictures, CATWOE diagrams, etc • Key elements: • People • Connections - people’s attitudes/motivations/ objectives in relation to system elements

16. Rich picture example of soft systems analytical technique ??????????? Blah blah blah …! Lectures Lecturer Students

17. 3. Some points to consider • Why use diagrams anyway? (When does text work better/worse?) • Selectivity (correctness and suitability of use) • “Logical” vs “physical” • Detail and comprehensibility: • Partitioning horizontally – how much can you (reasonably) fit on one page? • Partitioning vertically – how low do you go in terms of detail? (how deep the hierarchy) • Standards/conventions for symbols and meaning

18. Analytical techniques and system development approaches • Theoretically any technique could be used as part of any type of system development process • But in practice each technique originated with a particular development approach and tends to be associated with that approach • Process-oriented – (structured analysis and design, eg waterfall) • Data-oriented – (information engineering) • Object-oriented – prototyping/RAD environments • Soft systems – socio-technical methods

19. 4. Summary • There are many possible techniques for analysing an IS • Each technique provides a particular focus and perspective on the system • You need to be familiar with a variety of techniques, so you can choose which is appropriate to the situation and system development need