dr. stephania loizidou himona1 acsc 155 system analysis and design 1. introduction acsc 155 system...

Dr. Stephania Loizidou HimonaDr. Stephania Loizidou Himona 11

ACSC 155 ACSC 155 System Analysis and DesignSystem Analysis and Design

1. Introduction 1. Introduction


Information SystemsInformation Systems

What is a System?What is a System? A system is a set of components that A system is a set of components that interact to accomplish some purposeinteract to accomplish some purpose

Examples include the Economic systemExamples include the Economic systemthe Language systemthe Language systema Business and its partsa Business and its partse.g. Marketing, Sales, Research, e.g. Marketing, Sales, Research,

Shipping, Accounting, Shipping, Accounting, Government etc.Government etc.


INFORMATION SYSTEMINFORMATION SYSTEM

What is an Information System (I.S.)?What is an Information System (I.S.)?

INPUT OUTPUTPROCESS

FEEDBACK

INFORMATION SYSTEMINFORMATION SYSTEM


Information SystemInformation System

– Interrelated components working together to Interrelated components working together to collect, process, store and disseminate collect, process, store and disseminate information to support decision making, information to support decision making, coordination control analysis and visualisation in coordination control analysis and visualisation in an organisation. an organisation.


Information versus DataInformation versus Data Basic components:Basic components:

– InputInput

– OutputOutput

– ProcessingProcessing

– FeedbackFeedback

Computer-based I.S.Computer-based I.S.


What is Systems Analysis & Design?What is Systems Analysis & Design?

The process of examining a (business) situation with the The process of examining a (business) situation with the intent of improving it through better procedures and intent of improving it through better procedures and methods. methods. Distinguish between:Distinguish between:

- System Analysis- System Analysis - Process of gathering and - Process of gathering and interpreting facts, diagnosing problems, and using the interpreting facts, diagnosing problems, and using the facts to improve the system.facts to improve the system.

- Systems Design- Systems Design - Process of planning a new system - Process of planning a new system to replace or complement the old.to replace or complement the old.


AnalysisAnalysis specifies specifies whatwhat the system the system should do; should do;

DesignDesign states states howhow to achieve the to achieve the objective.objective.


SYSTEM ANALYSISSYSTEM ANALYSISOPORTUNITY TO IMPROVE A SYSTEMOPORTUNITY TO IMPROVE A SYSTEM

A A System development life cycle System development life cycle (SDLC)(SDLC) is a process by which systems is a process by which systems analysts, software engineers, analysts, software engineers, programmers, and end users build programmers, and end users build information systems and computer information systems and computer applications.applications.

It consists of 5 distinct stages.It consists of 5 distinct stages.


Systems Life CycleSystems Life Cycle


1.1. Problem Identification Problem Identification What is the problem?What is the problem? Terms of ReferenceTerms of Reference

Preliminary Analysis (Feasibility Preliminary Analysis (Feasibility Reports*)Reports*)

2.2. System AnalysisSystem AnalysisPriorization of the requirements Priorization of the requirements

for for solving the problem. The solving the problem. The emphasis is on the emphasis is on the

business, not business, not the computer the computer (what to do, not (what to do, not how to do how to do it).it).

Functional SpecificationFunctional Specification


**Feasibility Study Feasibility Study Advantages Vs Disadvantage Advantages Vs Disadvantage

TT Technical feasibilityTechnical feasibility (technically practical, staff, (technically practical, staff, expertise)expertise)

EE Economic feasibilityEconomic feasibilityIs it cost effective?Is it cost effective?

LL Law feasibilityLaw feasibilityIs it legal?Is it legal?

OO Operational feasibilityOperational feasibilityDoes it fulfill user requirements?Does it fulfill user requirements?To what degree?To what degree?Will the work environment change?Will the work environment change?How does users feel about such a solution?How does users feel about such a solution?

SS Schedule feasibilitySchedule feasibilityDesign and implementation in acceptable period of Design and implementation in acceptable period of time?time?


3.3. System DesignSystem Design

The evaluation of alternative problem The evaluation of alternative problem solutions and the detailed solutions and the detailed

specifications specifications of the final solution of the final solution computer-based. computer-based. Emphasis shifts from Emphasis shifts from the business to the the business to the computer solution computer solution (how to do it).(how to do it).

Detailed Systems SpecificationDetailed Systems Specification

LogicalLogical versus versus PhysicalPhysical Design. Design.


4.4. System ImplementationSystem ImplementationThe construction or assembly of the new The construction or assembly of the new

system system and the delivery of that system into and the delivery of that system into

“production” “production” (meaning “day-to-day” operation).(meaning “day-to-day” operation). Fully Documented systemFully Documented system

5.5. System Support and MaintenanceSystem Support and MaintenanceThe ongoing maintenance and enhancement The ongoing maintenance and enhancement

of of a system after it has been placed into a system after it has been placed into operation. This includes program operation. This includes program

maintenance maintenance and system and system

improvements.improvements. Test RunsTest Runs


Computer Assistant Software Computer Assistant Software Engineering (CASE)Engineering (CASE)

Automated case toolsAutomated case tools

Project Management tools and TechniquesProject Management tools and Techniques

PERT CHART (Project Evaluation and PERT CHART (Project Evaluation and Review Technique) Review Technique)

Gantt ChartGantt Chart


USERSUSERS

Direct Users (interact with the system)Direct Users (interact with the system) Indirect Users (initiate processes)Indirect Users (initiate processes) Administrative Users (deal with money)Administrative Users (deal with money) People involved in AnalysisPeople involved in Analysis

– Business Analysts (Identification, Feasibility, Analysis)Business Analysts (Identification, Feasibility, Analysis)– Systems Designers (Design)Systems Designers (Design)– Systems Analysts (Everything)Systems Analysts (Everything)– Analyst Programmers (Everything, or what they know)Analyst Programmers (Everything, or what they know)

What do Systems Analysts do?What do Systems Analysts do? What skills so they need?What skills so they need?


Objections to the life cycle modelObjections to the life cycle model– Time scale factorTime scale factor– Difficult to be understoodDifficult to be understood

An alternative approachAn alternative approach– Design by Design by PrototypingPrototyping


PrototypePrototype

A live-working A live-working

Requirements specified in advanceRequirements specified in advance

An iterative processAn iterative process

Valuable at various stages of the SDLCValuable at various stages of the SDLC


The prototype approachThe prototype approach


Comparison of the SDLC and the Prototype Comparison of the SDLC and the Prototype ApproachesApproaches

SDLCSDLCAdvantagesAdvantages DisadvantagesDisadvantages

Pre-defined stages (exactly what is Pre-defined stages (exactly what is required for each one)required for each one)

Takes too long time to complete Takes too long time to complete requirements might change over requirements might change over timetime

Guaranties effective end-resultGuaranties effective end-result Needs computerised literate Needs computerised literate (expertise) people(expertise) people

Experience in every step Experience in every step (consequence from 1(consequence from 1stst advantage) advantage)

The user sees only the end resultThe user sees only the end result

Viscous circle (close loop – you are Viscous circle (close loop – you are never finished with it)never finished with it)

Costs too muchCosts too much


PrototypePrototypeAdvantagesAdvantages DisadvantagesDisadvantages

Live-working system. The user is Live-working system. The user is actively involvedactively involved

User has to be able to User has to be able to criticise/suggest the system criticise/suggest the system computerised expertisecomputerised expertise

Interactive (you actually see stages Interactive (you actually see stages of it, and not only the end result of it, and not only the end result suggest alternatives as you go suggest alternatives as you go along – test its operationalong – test its operation

No pre-defined stagesNo pre-defined stages

Iterative (things happening in loops)Iterative (things happening in loops) Does not guarantee an effective Does not guarantee an effective end result (incomplete working end result (incomplete working system)system)

Can be used as a first attempt of a Can be used as a first attempt of a designdesign

It cannot handle big systemsIt cannot handle big systems

Library search for an ‘existing – Library search for an ‘existing – similar’ systemsimilar’ system

CostCost

dr. stephania loizidou himona1 acsc 155 system analysis and design 1. introduction acsc 155 system...

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