life cycle models (visual programming technologies)

8/13/2019 Life Cycle Models (Visual Programming Technologies)

1/35

Life Cycle Models

(Visual Programming Technologies)

CS3001 Presentation 1


2/35

The theoretical background

System Development Life CycleWhy we need a SDLC

Advantages of using and SDLCThe Waterfall ModelSpiral ModelLifecycle vs. Methodology

Methodology


3/35

Why we need a SDLC

Ease the process of building asystem

Avoid development problemsUnclear objectivesCost overrunsDevelopment delays

Avoid the system not meeting userrequirements


4/35

Advantages of a Life Cycle

Facilitate project reviewProvide a more efficient / effective

systemGuide the systems developmentImprove communications

Improve management and controlComputer-based support


5/35

Waterfall ModelProblem Definition

Requirement Analysis

System Design

System Development

System Testing

Implementation

Maintenance


6/35

Problem Definition

Project GoalsA broad statement of What the userexpects from the system

Project Bounds What areas the system effects andwhat areas remain the same

Project Limits Resource limits (Financial,technology, human, S/w, H/w)


7/35


The current systemWhat it does, and how it works

A Detail Model in subject termsWhat the new system will do, how itwill work

High level description of the system


8/35

System Design

Produce a detailed specification forthe new system

Here the description of the systemanalysis is converted in to a designwhich can be implemented


9/35

Steps in System Design

Select equipmentSpecify new programs or changes

to existing programsSpecify new database or changes toexisting databaseProduce detailed procedures(Detailed Design)


10/35

System Development

The Detailed design is convertedinto the system

Individual system components are builtand testedData and tools are used to build thesystemUser interfaces are developed and tried

by usersDatabase is initialized with data


11/35


12/35

Implementation

Installation of the system at theclient endRepresents the start of the systemsfunctioning into its real environment


13/35

Maintenance

Maintenance is a continuous processInvolves new modifications

Eliminate errors in the systemduring its working life.Fixing any bugs and problem foundby users

Tune the system to any variationsin its working environment


14/35

Problems with the Waterfall Model

Rigid design and inflexible procedureTop-down procedure

Real projects rarely follow the sequential flowthat the model proposes

One phase must be completed before the nextphase startsAt the beginning of most projects there isoften a great deal of uncertainty aboutrequirements and goals, and it is thereforedifficult for customers to identify these criteriaon a detailed level. The model does notaccommodate this natural uncertainty verywell.


15/35

Problems with the Waterfall Model

No phase can be repeatedAssumptions made in the earlyphases no longer holdSome of the early work isincompleteSomething was overlooked or notcompletely understood .


16/35

The Modified Waterfall Model

Problem Definition


System Design

System Development

System Testing

Maintenance


17/35

Spiral Model


18/35

Main phases in the Spiral Model

Requirement analysisDesign prototype

Develop and integrateAcceptances and testing


19/35

Life Cycle vs. Methodology

The software development processconsists of several well-definedsteps.When following a designmethodology, a designer can selectappropriate modeling method

related to each step


20/35


LIFE CYCLE STAGE

System Operation& Support

Using InformationTechnology

LIFE CYCLE STAGE

SystemDevelopment

Using SystemDevelopment

Methodologies

LifetimeOf a

System

A system life cycledivides the life of an

information systeminto two majorStages1. Systems

Development2. Systems

operation andsupport.


21/35


A system development methodologyis a very formal and precise systemdevelopment process that defines

A set of activitiesMethodsBest practicesDeliverables

Automated tools


22/35

System Development methodology

A System Development methodology(Process) has some general principles.P1: Get the owner and User InvolvedP2: Use a problem-solving approach

Study and understand the problem and itscontextDefine the requirement of a suitable solution.Identify candidate solutions and select the bestsolution.Design and/or implement the solution.Observe and evaluate the solutions impact,and refine the solution accordingly


23/35


P3: Establish phases and activitiesPreliminary investigationProblem analysisRequirement analysisDecision analysisDesign

ConstructionImplementation


24/35


P4: Establish standardsDocumentationQualityAutomated ToolsInformation technology


25/35


P5: Justify systems as capitalinvestments

Cost effectivenessRisk management


26/35


P6: Dont be afraid to cancel or revisescope

Cancel the project if it is no longer

feasibleIf project scope is to be increased,reevaluate and adjust the cost andscheduleIf the project budget and schedule arefrozen and not sufficient to cover allproject objectives, reduce the scope


27/35

System development methodology

P7: Divide and conquerWe divide a system into subsystemand components

Easily to conquer the problemEasy to build a large problem


28/35


P8: Design systems for growth andchange

Correcting simple mistakesTo redesigning the system toaccommodate changing technologyTo making modification to support

changing user requirements.


29/35

Development Process

MethodologyModeling Methods or Techniques

Tools


30/35

Methodology

Provides the frameworkHas a predefined set of steps

Ensures that systems are built inthe most effective wayE.g. SSADM, RUP

Uses tools and modeling methods


31/35

Modeling Methods

A set of techniques used toimplement a Methodology

Data Flow DiagramsEntity Relationship DiagramsStructure Charts etc.


32/35

System Development methodologies

Supported by Modeling Methods orTechniques

Techniques used to implement theMethodologyProvides the descriptions of thebusiness system requirements fromvarious view points


33/35

Tools

Software systemsAssists analysts and designer to

build information systemse.g. Easy Case, Rational Rose, MS Visio

Supported by Tools.They will not replace Systems Analysts.


34/35

Methodology

Rational Unified Process

Modeling Method orTechnology

Tools

Use Case DiagramsClass Diagrams

Rational SuitRational ROSE


35/35

Summary

System Life CyclesWhy we need themAdvantages

Waterfall ModelFaults with this model

Spiral ModelSD Life Cycle vs. SD MethodologySystem Development Methodology

life cycle models (visual programming technologies)

Documents