Approaches Sdl c

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Approaches to System DevelopmentApproaches to System Development

Information Systems Analysis and Design

Shah Masud


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Lecture OutlineLecture Outline

Systems Development Life CycleSystems Development Life Cycle

Phases and Activities in the SDLCPhases and Activities in the SDLC

Variations of the SDLC modelsVariations of the SDLC models

Selecting the appropriate modelSelecting the appropriate model

MethodologiesMethodologies of the SDLCof the SDLC

Traditional Approach to SDLCTraditional Approach to SDLC

Information ngineering Approach to SDLCInformation ngineering Approach to SDLC

O!"ect#Oriented Approach to SDLCO!"ect#Oriented Approach to SDLC

$apid Application Development$apid Application Development

Current trends in the SDLCCurrent trends in the SDLC

CAS ToolsCAS Tools2Shah Masud


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Systems development life cycleSystems development life cycle(SDLC)

Provides overall frame%or&overall frame%or&for managing systems

development process

Two main approaches to SDLC

Predictive approachPredictive approach assumes project can e

planned out in advanceAdaptive approachAdaptive approach more fle!ile" assumes project

cannot e planned out in advance

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Predictive vs' Adaptive Approach to the SDLCPredictive vs' Adaptive Approach to the SDLC

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Systems Life CycleSystems Life Cycle

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Activities of ach SDLC PhaseActivities of ach SDLC Phase

Predictive or adaptive approach use SDLC

#ctivities of each &phase' are similar

Phases are not always se$uential

Phases can overlap

#ctivities across phases can e done withinan iteration

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Design ActivitiesDesign Activities

Design and integrate the networ%

Design the application architecture

Design the user interfaces

Design the system interfaces

Design and integrate the dataase

Prototype for design details

Design and integrate system controls 11Shah Masud


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Implementation ActivitiesImplementation Activities

Construct software components

-erify and test

Convert data

Train users and document the system

.nstall the system

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Overlap of activitiesOverlap of activities

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++,aterfall- Approach0 pros and cons,aterfall- Approach0 pros and cons

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The two key advantages of the waterfall model:Identifying system requirements long before programming beginsIt minimizes changes to the requirements as the project proceeds

The key disadvantages:The design must be completely specified on paper before programming beginsA long time elapses between the completion of the system proposal in the analysis

phase and the delivery of the system (usually many months or years)

A paper document is often a poor communication mechanism! so importantrequirements can be overloo"ed in the hundreds of pages of documentation

#sers rarely are prepared for their introduction to the new system! which occurs longafter the initial idea for the system was introduced

If the project team misses important requirements! e$pensive post%implementationprogramming may be needed

A system may require significant rewor" because of changes in business environmentsince the time the analysis phase occurred It means going bac" to the initial phasesand following the changes through each of the subsequent phases in turn

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The Parallel ModelThe Parallel Model

TheParallel Modelattempts to address the prolem of longdelays etween the analysis phase and the delivery of thesystem2

.nstead of doing the design and implementation in se$uence"

it performs a general design for the whole system and thendivides the project into series of distinct suprojects that cane designed and implemented in parallel

3nce all suprojects are complete" the final integration of theseparate pieces is delivered

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The Parallel ModelThe Parallel Model

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Parallel Model0 pros and consParallel Model0 pros and cons

Primary advantages0

Can reduce the schedule time re$uired to deliver a system

There is less chance of changes in the usiness environmentcausing rewor%

1ey disadvantages0

Still suffers from prolems caused y paper documentation

# new prolem4 sometimes the suprojects are notcompletely independent5 design made in one suproject may

affect another and the end of the project may re$uiresignificant integrative efforts

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Iteration of System Development ActivitiesIteration of System Development Activities

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Phased Development ModelPhased Development Model

+rea%s the overall system into a series of versionsthat are developedse$uentially

The analysis phase identifies the overall system concept2 The project team"users and system sponsors categorie the re$uirements into a series ofversions

The most important and fundamental re$uirements are undled into thefirst version of the system2 The analysis phase then leads into design andimplementation" ut only with the set of re$uirements identified forversion 9

3nce version 9 is implemented" wor% egins on version :2 #dditionalanalysis is performed on the asis of the previously identified re$uirementsand comined with new ideas and issues that arose from users; e!periencewith version 92

-ersion : then is designed and implemented" and wor% immediately eginson the ne!t version2 This process continues until the system is complete

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Phased Model0 pros and consPhased Model0 pros and cons

Advantages0


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Criteria for SelectingCriteria for Selecting

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&larify of user requirements'ometimes the user requirements are unclear or subject tochange rototyping and throwaway prototyping are more appropriate models forsuch situations! because they provide prototypes for user to interact with at earlystages of the '*&

+amiliarity with Technology,hen the system will use new technology! which is

unfamiliar for the analysts and programmers (eg the first ,eb%based project with-ava)! it increases the ris"s Application of the new technology as early as possiblewill improve the chance of success Throwaway prototyping is particularlyappropriate for this situation since it e$plicitly encourages the developers to developdesign prototypes for areas with high ris"s hased model is good as well because itcreates opportunities to investigate the technology in some depth before the design is

complete'ystem &omple$ity&omple$ systems require careful and detailed analysis and designThrowaway prototyping is particularly well suited to such situation! but prototypingis not The traditional structured methodologies can handle comple$ systems! butwithout the ability to get the system or prototypes into users. hands early on! some"ey issues may be overloo"ed /ven though the phased model enables users tointeract with the system early in the process

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Criteria for SelectingCriteria for Selecting

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'hort time schedulesrojects with short time schedules are well suited for 0A models as

far as they are designed to increase the speed of development rototyping and phases

development are e$cellent choices because they best enable the project team to adjust the

functionality in the system If the project schedule starts to slip! it can be readjusted by

removing functionality from the version or prototype under development The waterfall

model is the worst choice! because it does not allow for easy schedule changes

'chedule visibility1ne of the greatest challenges in systems development is "nowing

whether a project is on schedule This is particularly true of the structured methods

because design and implementation occur at the end of the project The 0A models

move many of the critical design decisions to an earlier point in the project to help project

managers to recognize and address ris" factors and "eep e$pectations in chec"

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Some Models 5sed in SDLCSome Models 5sed in SDLC

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Techni.uesTechni.ues

Techni$ues

Collection of guidelines that help analysts completea system development activity or tas%

Can e step8y8step instructions or just generaladvice

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Some Techni.ues 5sed in SDLCSome Techni.ues 5sed in SDLC

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Three Structured Programming ConstructsThree Structured Programming Constructs

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Top#Do%n ProgrammingTop#Do%n Programming

Divides comple! programs into hierarchy of

modules

The module at top controls e!ecution y &calling'lower level modules

/odular programming

Similar to top8down programming

3ne program calls other programs to wor%

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Top#Do%n or Modular ProgrammingTop#Do%n or Modular Programming

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Structured DesignStructured Design

Techni$ue developed to provide design guidelines7hat set of programs should e

7hat program should accomplish

0ow programs should e organied into a hierarchy

/odules are shown with structure chart

/ain principle of program modulesLoosely coupled module is independent of othermodules

0ighly cohesive module has one clear tas%

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Structure Chart Created 5singStructure Chart Created 5sing


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Structure Chart Created 5singStructure Chart Created 5sing

Structured Design Techni.ueStructured Design Techni.ue

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Structured AnalysisStructured Analysis

Define what system needs to do (processing

re$uirements)

Define data system needs to store and use (datare$uirements)

Define inputs and outputs

Define how functions wor% together to accomplish tas%s

Data flow diagrams (D6D) and entity relationship diagrams

(,D) show results of structured analysis

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Data 4lo% Diagram (D4D* Created 5singData 4lo% Diagram (D4D* Created 5sing

Structured Analysis Techni.ueStructured Analysis Techni.ue

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ntity#$elationship Diagram ($D* Created 5singntity#$elationship Diagram ($D* Created 5sing

Structured Analysis Techni.ueStructured Analysis Techni.ue

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Structured Analysis Leads to Structured DesignStructured Analysis Leads to Structured Design

and Structured Programmingand Structured Programming

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Information ngineering (I*Information ngineering (I*

6ocus on strategic planning to identify all the organiation informationneeds (the application architecture plan)" data modeling" and automatedtools

/ore focused on data itself than the structured approach2 +ut just as thestructural approach includes data re$uirements" . includes processes" too

The processing model of information engineering" the process dependencydiagram" is similar to a data flow diagram" ut it focuses more on whichprocesses are dependent on other processes and less on data inputs andoutputs

Provides more complete life cycle support through the use of an integratedC#S tools (help to automate systems development5 final program code cane generated automatically y the C#S tools)

+ecame popular on large8mainframe systems in the 9@AB;s" less used in the9@@B;s on smaller des%top systems (ut concepts still used y planning andemphasis on data modeling)

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O!"ect#Oriented Approach to SystemsO!"ect#Oriented Approach to Systems

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O!"ect#Oriented Approach (continued*O!"ect#Oriented Approach (continued*

3ject8oriented analysis (33#)

Defines types of ojects users deal with

Shows use cases are re$uired to complete tas%s

3ject8oriented design (33D)

Defines oject types needed to communicate with people and devices in system

Shows how ojects interact to complete tas%s

,efines each type of oject for implementation with specific language of

environment

3ject8oriented programming (33P)

7riting statements in programming language to define what each type of oject

does

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Class Diagram Created During OO AnalysisClass Diagram Created During OO Analysis

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SDLC VariationsSDLC Variations

/any variations of SDLC in practice

+ased on variation of names for phases

Fo matter which one" activities1tas%s are similar Some increase emphasis on people

Gser8centred design" participatory design

Socio8technical systems

Some increase speed of development

,apid application development (,#D)

Prototyping66Shah Masud

Rapid Application DevelopmentRapid Application Development


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Rapid application development-0AD. is one of the+ariations of SD

Aims to s!eed u! the de+elo!ment !ro&ess%

/merged in the 199s as an attem!t to address *oth

$ea,nesses of the $aterfall de+elo!ment" long de+elo!menttimes and the diffi&ulty in understanding a system from !a!er*ased des&ri!tion%

Methods:

'(ries to s!eed u! the a&ti+ities in ea&h !hase -e%g% s!eeding theanalysis !hase *y s&heduling intensi+e meetings of ,ey !arti&i!ants to

get information gathered and de&isions made ra!idly.'sing iterati+e de+elo!ment -e%g% s!iral life &y&le model. to s!eed u!the !ro&ess of getting to design and im!lementation

'uilding !rototy!es of the system during analysis and design !hases%It im!ro+es understanding of the system re)uirements'sing CASE-&om!uteraided system engineering. toolsto s!eed u!

the analysis design and im!lementation !hases

Rapid Application DevelopmentRapid Application Development

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Current Trends in DevelopmentCurrent Trends in Development

/ore adaptive approaches

The Gnified Process (GP)

!treme Programming (HP)

Scrum

Details on each in Chapter 9I

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The 5nified Process (5P*The 5nified Process (5P*

3ject8oriented development approach

3ffered y .+/ 1 ,ational

+ooch" ,umaugh" acoson

Gnified /odeling Language (G/L) used primarily for modeling

G/L can e used with any 33 methodology

GP defines four life cycle phases

.nception" elaoration" construction" transition

Defines wor%flows within each phase4 usiness modeling" re$uirements

modeling" analysis and design" implementation" testing" development"configuration and change management" and project management

.nvolves roles of4 designer" use case specifier" systems analyst"

implementer" architect

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Th 5 ifi d P (5P* ( ti d*The 5nified Process (5P* (continued*


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The 5nified Process (5P* (continued*The 5nified Process (5P* (continued*

,einforces si! est practices

Develop iteratively

Define and manage system re$uirements

Gse component architectures

Create visual models

-erify $uality

Control changes 71Shah Masud

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6treme Programming (7P*6treme Programming (7P*

,ecent" lightweight" development approach to %eep process simple

and efficient

Descries system support needed and re$uired system functionality

through informal user stories

0as users descrie acceptance tests to demonstrate defined

outcomes

,elies on continuous testing and integration" heavy user

involvement" programming done y small teams

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Vi l M d li T l $ it C t i AllVi l M d li T l $ it C t i All


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Visual Modeling Tool $epository Contains AllVisual Modeling Tool $epository Contains All

System InformationSystem Information

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CAS Tools0 6amplesCAS Tools0 6amples

Microsoft Visio

?a drawing tool suitale for aout any system model

?comes with a collection of drawing templates (incl2

symols used in a variety of usiness and engineeringapplications4 flowcharts" D6Ds" ,Ds" G/L diagrams)

?provides only a limited repository for storingdefinitions and descriptions of diagram elements" utnot a complete repository for a system developmentproject2

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CAS T l l ( t8d*CAS Tools0 6amples (cont8d*


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CAS Tools0 6amples (cont8d*CAS Tools0 6amples (cont8d*

Oracle Designer?a tool set for recording definitions and automating the rapid

constructions of fle!ile" graphical client#server applications

?integrated with 3racle Developer (a tool for creating *G.applications)

?includes a complete repository" diagramming and code8generating capailities

?an integrated C#S tool that supports traditional approachtosystem development (process modeler" function8hierarchydiagrammer" data flow diagrammer" entity8relationshipdiagrammer)

?Design Transformer and Design ditor produce diagrams alongwith the dataase and application logic

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Oracle DesignerOracle Designer0 4ront Panel screen0 4ront Panel screen

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Oracle DesignerOracle Designer0 ntity#$elationship Diagrammer0 ntity#$elationship Diagrammer

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TogetherSoft

?The most recent concept of round-trip engineering

?allows synchroniing the graphical models (such as class

diagram) with generated program code (automation inoth directions round trip)2

?.f the program code is changed" the class diagram isupdated and contra versa" if the class diagram ischanged" the program code is updated2

?Together uses G/L diagrams with several differentprogramming languages

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TogetherTogethersho%ing a class diagram %ithsho%ing a class diagram %ith

synchroni/ed 3ava source codesynchroni/ed 3ava source code

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CAS T l l ( t8d*CAS T l l ( t8d*


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Embarcadero Describe

?a new product that include modeling andround8trip engineering features

?provides fle!ile G/L modeling capailities foranalysis and design

?provides round8trip engineering with several

ava development tools (+uilder and Sum6orte)

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