Sd Week2 Slides

8/10/2019 Sd Week2 Slides

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SYSTEM DESIGN

Slides adapted from Whitten & Bentley by Dr. YasserEL Man!ala"y


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System Desi#nLearning objectives

Describe the design phase in terms of yo$r

2

.

Identify and differentiate bet"een several systemsdesign strategies .

Des%ribe the desi#n phase tas s in terms of a%omp$ter based sol$tion for an in ho$sede'elopment pro(e%t.


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System Desi#n +pproa%hesModel Dri'en

Modern str$%t$red desi#nInformation en#ineerin#

,rotot in

4

-b(e%t oriented

+D

/+D


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Model Dri'en +pproa%hes

Model-driven strategy * a systemdesi#n approa%h that emphasi!esdra"in s stem models to do%$ment

5

te%hni%al and implementation aspe%tsof a system.


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Model Dri'en +pproa%hes * Modern

Str$%t$red Desi#nModern structured design * a system desi#n te%hni0$e

that de%omposes the system1s pro%esses intomana#eable %omponents.Synonyms are2 top-down program design and structured

ro rammin .

Desi#n in a top do"n hierar%hy of mod$lesEasier to implement and maintain 3%han#e4.Mod$les sho$ld be hi#hly %ohesi'e

+%%omplish one f$n%tion onlyMod$les sho$ld be loosely %o$pled

Minimally dependent on one another


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Str$%t$re 5hart!


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Str$%t$re 5hartsStructure charts are $sed to spe%ify the hi#h le'el

desi#n6 or ar%hite%t$re6 of a %omp$ter pro#ram.sho"s the data and %ontrol information flo"s bet"eenthe mod$les.

"

top do"n mod$lar desi#n tools0$ares representin# the different mod$les in thesystem

lines represent the %onne%tion and or o"nershipbet"een a%ti'ities and s$ba%ti'ities


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Str$%t$re 5harts#

$ote% Data &low vs' control &low


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Model Dri'en +pproa%hes *

Information En#ineerin#(n&ormation engineering )(*+ * a model dri'en and

data %entered6 b$t pro%ess sensiti'e te%hni0$e forplannin#6 analy!in#6 and desi#nin# informationsystems. IE models are pi%t$res that ill$strate and

,

syn%hroni!e the system1s data and pro%esses.The primary tool of IE is a data model diagram .


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,hysi%al Entity elationship Dia#ram,,


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,rototypin#.rototype * a small s%ale6 in%omplete6 b$t "or in# sample of adesired system

Iterati'e pro%ess in'ol'in# a %lose "or in# relationship bet"een thedesi#ner and the $sers.

/ey 0ene&its 2

,2

En%o$ra#es and re0$ires a%ti'e end $ser parti%ipation.Iteration a%%ommodates end $sers "ho tend to %han#e their minds.Endorses philosophy that end $sers "on1t no" "hat they "ant $ntil theysee it.+%ti'e model that end $sers %an intera%t "ith.Errors %an be dete%ted earlier.5an in%rease %reati'ity as it allo"s for 0$i% er $ser feedba% .+%%elerates se'eral phases of the life %y%le.


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,rototypin#Disadvantages and .it&alls%

En%o$ra#es 7%ode6 implement6 and repair8 life %y%le that %a$semaintenan%e ni#htmares.

Still need systems analysis phases6 b$t so easy to s ip.

5annot %om letel s$bstit$te a rotot e for a a er s e%ifi%ation li e

,3

ar%hite%t "itho$t a bl$eprint4.N$mero$s desi#n iss$es are not addressed by prototypin#.

-ften leads to premat$re %ommitment to a desi#n.

S%ope and %omple9ity of the system %an e9pand o$t of %ontrol.

5an red$%e %reati'ity in desi#ns .

-ften s$ffer from slo"er performan%e be%a$se of lan#$a#e%onsiderations 3rapidly be%omin# a non iss$e4.


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Sample ,rototype S%reen,4


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-b(e%t -riented Desi#n1bject-oriented design )11D+ te%hni0$es are $sed to

refine the ob(e%t re0$irements definitions identifiedearlier d$rin# analysis6 and to define desi#n spe%ifi%ob(e%ts.

,5

E9tension of ob(e%t oriented analysis+ttempt to eliminate the separation of %on%erns abo$tdata and pro%ess.


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apid +ppli%ation De'elopment 3 +D4

apid application development ) D+ * a systems

desi#n approa%h that $tili!es str$%t$red6prototypin#6 and /+D te%hni0$es to 0$i% ly de'elops stems.

,

The mer#er of 'ario$s str$%t$red te%hni0$es toa%%elerate systems de'elopment

Data dri'en information en#ineerin#

,rototypin#/oint appli%ation de'elopment


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/oint +ppli%ation De'elopment 3/+D4

oint pplication Development ) D+ is a

te%hni0$e that %omplements other systems analysisand desi#n te%hni0$es by emphasi!in#participative development amon# system o"ners6$sers desi ners and b$ilders.

,!

D$rin# the /+D sessions for systems desi#n6 thesystems desi#ner "ill ta e on the role of fa%ilitator

for possibly se'eral f$ll day "or shops intendedto address different desi#n iss$es anddeli'erables.


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System Desi#n Tas s :or In ;o$se

De'elopmentDesi#n the +ppli%ation +r%hite%t$re 35h


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System Desi#n Tas s :or In ;o$se

De'elopment,#


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e'ie" $estions

4 What are the fi'e hi#h le'el tas s in'ol'ed in

%ond$%tin# system desi#n for a de'elopment

pro(e%t to be b$ilt in ho$se)?4 What is :i#$re


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e'ie" $estions2,

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