1. Dr. Stephania Loizidou Himona1 ACSC 155 System Analysis and Design 1. Introduction ACSC 155 System Analysis and Design 1. Introduction

2. Dr. Stephania Loizidou Himona2 Information Systems What is a System? A system is a set of components that interact to accomplish some purpose Examples include the Economic system the Language system a Business and its parts e.g. Marketing, Sales, Research, Shipping, Accounting, Government etc.

3. Dr. Stephania Loizidou Himona3 INFORMATION SYSTEM What is an Information System (I.S.)? What is an Information System (I.S.)? INPUTOUTPUTPROCESS FEEDBACK INFORMATION SYSTEM

4. Dr. Stephania Loizidou Himona4  Information System –Interrelated components working together to collect, process, store and disseminate information to support decision making, coordination control analysis and visualisation in an organisation.

5. Dr. Stephania Loizidou Himona5  Information versus Data  Basic components: –Input –Output –Processing –Feedback  Computer-based I.S.

6. Dr. Stephania Loizidou Himona6 What is Systems Analysis & Design?  The process of examining a (business) situation with the intent of improving it through better procedures and methods. Distinguish between: - System Analysis - Process of gathering and interpreting facts, diagnosing problems, and using the facts to improve the system. - Systems Design - Process of planning a new system to replace or complement the old.

7. Dr. Stephania Loizidou Himona7  Analysis specifies what the system should do;  Design states how to achieve the objective.

8. Dr. Stephania Loizidou Himona8 SYSTEM ANALYSIS OPORTUNITY TO IMPROVE A SYSTEM  A System development life cycle (SDLC) is a process by which systems analysts, software engineers, programmers, and end users build information systems and computer applications. It consists of 5 distinct stages.

9. Dr. Stephania Loizidou Himona9 Systems Life Cycle

10. Dr. Stephania Loizidou Himona10 1.Problem Identification What is the problem? Terms of Reference Terms of Reference Preliminary Analysis (Feasibility Reports*) Preliminary Analysis (Feasibility Reports*) 2.System Analysis Priorization of the requirements for solving the problem. The emphasis is on the business, not the computer (what to do, not how to do it). Functional Specification Functional Specification

11. Dr. Stephania Loizidou Himona11 *Feasibility Study Advantages Vs Disadvantage *Feasibility Study Advantages Vs Disadvantage  TTechnical feasibility (technically practical, staff, expertise)  EEconomic feasibility Is it cost effective?  LLaw feasibility Is it legal?  OOperational feasibility Does it fulfill user requirements? To what degree? Will the work environment change? How does users feel about such a solution?  SSchedule feasibility Design and implementation in acceptable period of time?

12. Dr. Stephania Loizidou Himona12 3.System Design The evaluation of alternative problem solutions and the detailed specifications of the final solution computer-based. Emphasis shifts from the business to the computer solution (how to do it). Detailed Systems Specification Logical versus Physical Design.

13. Dr. Stephania Loizidou Himona13 4.System Implementation The construction or assembly of the new system and the delivery of that system into “production” (meaning “day-to-day” operation). Fully Documented system 5.System Support and Maintenance The ongoing maintenance and enhancement of a system after it has been placed into operation. This includes program maintenance and system improvements. Test Runs

14. Dr. Stephania Loizidou Himona14  Computer Assistant Software Engineering (CASE) Automated case tools Project Management tools and Techniques PERT CHART (Project Evaluation and Review Technique) Gantt Chart

15. Dr. Stephania Loizidou Himona15 USERS  Direct Users (interact with the system)  Indirect Users (initiate processes)  Administrative Users (deal with money)  People involved in Analysis –Business Analysts (Identification, Feasibility, Analysis) –Systems Designers (Design) –Systems Analysts (Everything) –Analyst Programmers (Everything, or what they know)  What do Systems Analysts do?  What skills so they need?

16. Dr. Stephania Loizidou Himona16  Objections to the life cycle model –Time scale factor –Difficult to be understood  An alternative approach –Design by Prototyping

17. Dr. Stephania Loizidou Himona17 Prototype  A live-working  Requirements specified in advance  An iterative process  Valuable at various stages of the SDLC

18. Dr. Stephania Loizidou Himona18 The prototype approach

19. Dr. Stephania Loizidou Himona19 Comparison of the SDLC and the Prototype Approaches SDLC AdvantagesDisadvantages Pre-defined stages (exactly what is required for each one) Takes too long time to complete  requirements might change over time Guaranties effective end-result Needs computerised literate (expertise) people Experience in every step (consequence from 1 st advantage) The user sees only the end result Viscous circle (close loop – you are never finished with it) Costs too much

20. Dr. Stephania Loizidou Himona20 Prototype AdvantagesDisadvantages Live-working system. The user is actively involved User has to be able to criticise/suggest the system  computerised expertise Interactive (you actually see stages of it, and not only the end result  suggest alternatives as you go along – test its operation No pre-defined stages Iterative (things happening in loops) Does not guarantee an effective end result (incomplete working system) Can be used as a first attempt of a design It cannot handle big systems Library search for an ‘existing – similar’ system Cost