MIS Development BBA (IT) 6 th
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Transcript of MIS Development BBA (IT) 6 th
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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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Object-Oriented MethodsObject-Oriented Methods
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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Object-Oriented MethodsObject-Oriented Methods
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