MIS Development BBA (IT) 6 th

© Farhan Mir© Farhan Mir

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MIS DevelopmentMIS DevelopmentBBA (IT) 6BBA (IT) 6thth (Lectures 222324)(Lectures 222324)(Information System (Information System Development Development Methodologies)Methodologies)

Course Lecturer: Farhan MirCourse Lecturer: Farhan Mir


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A methodology is ......A methodology is ......

a pompous word for “method”

investigation, research and discourse about methods

a set of techniques, tools, methods with some underlying philosophy


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Information Systems Information Systems Development MethodologiesDevelopment Methodologies

Structured Analysis, Design and Implementation of Information Systems (STRADIS)Yourdon Systems Method (YSM)Information Engineering (IE)Structured Systems Analysis and Design Methodology (SSADM)MeriseJackson Systems Development (JSD)Object-oriented AnalysisInformation Systems Work and Analysis of Changes (ISAC)Effective Technical and Human Implementation of Computer-based Systems (ETHICS)Soft System Methodology (SSM)MultiviewProcess InnovationRapid Application Development (RAD)KADSEuromethod


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Some methodologies ...... Some methodologies ...... with examples of specific methodswith examples of specific methods

Structured methodologiesYourdon, SSDAM, Ward-MellorYourdon, SSDAM, Ward-Mellor

Object-oriented methodologiesShlaer-MellorShlaer-Mellor

Soft systems methodologiesEthics, MultiviewEthics, Multiview


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Some ToolsSome Tools

ERDsDFDsRich picturesSTDsStructure chartsFormal logicsObject models

Prototypes

ELHs

JSP

Normalisation

Data dictionaries

PDL

Decision tables / trees


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Each methodology will use Each methodology will use several of these toolsseveral of these tools

with different emphasis, for different reasons, in a different order…...


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New methodologies New methodologies evolves becauseevolves because

perceived weaknesses in all other methodologies

changed and improved technologiescase, programming languages, hardwarecase, programming languages, hardware

changed environments, markets and needs

trends, fashion, band-wagon, legislation etc


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A quick run through some A quick run through some methodologies (and methodologies (and methods)methods)What led to their rise, then to their

fall; what were their tools and philosophies ?


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Structured MethodsStructured Methods

Probably the first methodology, after the so-called Test-and-Build i.e. “hacking”


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Structured MethodsStructured Methods

Structured analysis / design / programming

started in large-scale, stable, centralised corporate DP on mainframes using COBOL

“waterfall” life cycletop-down / functional decomposition


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Structured Methods ToolsStructured Methods Tools

DFDs

Structure Charts

ERDs

Data dictionaries


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Structured DesignStructured DesignTechnique developed to provide design guidelines

What set of programs should beWhat set of programs should beWhat program should accomplishWhat program should accomplishHow programs should be organized into a How programs should be organized into a hierarchyhierarchy

Modules are shown with structure chartMain principle of program modules

Loosely coupled – module is independent Loosely coupled – module is independent of other modulesof other modulesHighly cohesive – module has one clear Highly cohesive – module has one clear tasktask


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Structure Chart Created Using Structure Chart Created Using Structured Design TechniqueStructured Design Technique


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Structured AnalysisStructured Analysis

Define what system needs to do (processing requirements)

Define data system needs to store and use (data requirements)

Define inputs and outputs

Define how functions work together to accomplish tasks

Data flow diagrams and entity relationship diagrams show results of structured analysis


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Data Flow Diagram (DFD) Data Flow Diagram (DFD) created using Structured created using Structured Analysis Technique Analysis Technique


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Entity-Relationship Diagram (ERD) Entity-Relationship Diagram (ERD) created using the Structured Analysis created using the Structured Analysis techniquetechnique


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Structured Analysis Leads to Structured Analysis Leads to Structured Design and Structured Structured Design and Structured ProgrammingProgramming


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Problems with Structured Problems with Structured MethodsMethods

“Paralysis-by-analysis” / “Victorian novel”

Increasingly unstable requirements : they change quicker and quicker

validation : customers / users don’t understand DFDs, ERDs etc

verification : lurch from one notation to the next


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Problems with Structured Problems with Structured MethodsMethods

lack of precision, completeness, consistency etc : much natural language is used in Structured Methods

lack of user involvement

feasibility sometimes poorly identified


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More Problems with More Problems with Structured MethodsStructured Methods

Structured methods merely turn a big bit of vague text into small bits of vague text embedded in an ambiguous DFDEven if the structured analysis is provably correct, doesn’t mean the design and source code will be ! Or the machine code !


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Soft SystemsSoft Systems

One response to the failings of Structured Methods


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OriginsOrigins

Structured methods deal with problems; organisations have difficultiesMost information processing systems

have substantial human / social componentshave substantial human / social components

are embedded in social organisationsare embedded in social organisations

Customers and users have partial and conflicted views on their problems


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Soft Systems ToolsSoft Systems Tools

Based on systems theoryholistic not reductionistholistic not reductionist

subjective not objectivesubjective not objective

fuzzy not well-definedfuzzy not well-defined

purpose, boundaries, componentspurpose, boundaries, components

iterative


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Soft Systems ToolsSoft Systems Tools

Root definitionprecise verbal description of the essence of the precise verbal description of the essence of the processesprocesses

CATWOE

Rich picturesto build and check a “conceptual model” that form basis to build and check a “conceptual model” that form basis of information systemsof information systems


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Soft SystemsSoft Systems

Can begrafted onto “front-end” of hard systems grafted onto “front-end” of hard systems methodsmethods

have hard systems methods embedded within have hard systems methods embedded within themthem

are used increasingly


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Object-Oriented MethodsObject-Oriented Methods

Another response to the failings of Structured Methods


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Grew out of programmingeg Smalltalk, Simula

Originally technical and academicIntuitive : world consists of “things”, not functionsOffers framework for re-use

hence quicker quality

Now have industrial-strength methods


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Assume solution-domain will be entirely computer-based

Use one notation throughout life-cycle


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Object-Oriented Tools Object-Oriented Tools

Object models an enhanced ERDan enhanced ERD

Dynamic modelHarel charts Harel charts

Process modelDFDsDFDs

Documents

MIS Development BBA (IT) 6 th