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Chapter 3
Database SystemDevelopment Lifecycle
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Chapter Objectives…
Main components of an information system
Main stages of the Database System
Development Lifecycle (DSDLC) Main phases of database design:
conceptual, logical and physical design
ypes of criteria used to evaluate a D!MS
"o# to evaluate and select a D!MSs
$endall % $endall Copyright & '' by rentice "all, *nc+ -'
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Introduction
he .Soft#are Crisis/ 0 .soft#are depression/ 1-2 do not meet their performance goals4
5bout 1 are delivered late and over budget4
5round 6 fail or are abandoned4
7nder 6 fully address training and s8illsre9uirements4
Less than ' properly integrate enterprise and
technology ob;ectives4
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Continue…
Ma;or reason for the failure of soft#are pro;ects:
Lac8 of a complete re9uirements speci=cation
Lac8 of an appropriate developmentmethodology4
oor decomposition of design intomanageable components+
5s a solution to these problems, a structuredapproach to the development of a soft#are calledInformation Systems Lifecycle (ISLC) orSoftware Development Lifecycle (SDLC)"o#ever, #hen the soft#are being developed is a
database system the lifecycle is more speci=callyreferred to as Database System Development-6
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!he Information SystemLifecycle
*nformation System 0 the resources thatenable the collection, management, controland dissemination of information throughoutan organi>ation+
2?, database system gradually replace=le-based system as part of anorgani>ation@s *nformation System (*S)infrastructure
Computer-based *nformation System 0includes database, database soft#are,application soft#are, computer hard#are,and personnel using and developing the-
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!he Information SystemLifecycle
Database 0 fundamental component of aninformation system and its development andusage should be vie#ed from theperspective of the #ider re9uirements of theorgani>ation+
-A
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!he Database SystemDevelopment Lifecycle
Stages of Database System Development Lifecycle
Database lanning
System De=nition
Be9uirements collection and analysis
Database design
D!MS selection (optional)
5pplication design
rototyping (optional)
*mplementation
Data conversion and loading
esting
perational Maintenance
-?
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Database "lannin#
he management activities that allo# the stages ofthe database system development lifecycle to bereali>ed as eciently and eEectively as possible+
Database planning must be integrated #ith theoverall *S Strategy of the organi>ation+ hreemain issues involved in formulating an *Sstrategy:
*denti=cation of enterprise plans and goals
#ith subse9uent determination ofinformation needs+
Fvaluation of current information system todetermine eGisting strengths and#ea8nesses4
5ppraisal of * opportunities that mightield com etitive advanta e+
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System De$nition
Describes the scope and boundaries of thedatabase system and the ma;or user vie#s+
7ser Hie#s 0 De=ne #hat is re9uired of a
database system from the perspective of aparticular ;ob role (such as Manager orSupervisor) or enterprise application area(such as mar8eting, personnel, or stoc8
control)
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%e&uirements Collection and'nalysis
Be9uirements Collection and 5nalysis 0 theprocess of collecting and analysinginformation about the part of the
organi>ation that is to be supported by thedatabase system, and using this informationto identify the re9uirements for the ne#system+
his stage involves the collection andanalysis of information about the part ofthe enterprise to be served by thedatabase+
Iact =nding techni9ues - #ay of gathering-
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%e&uirements Collection and'nalysis
FGample of information being gather foreach ma;or user vie#
5 description of the data used or
generated4 he details of ho# the data is to be
used or generated4
5ny additional re9uirements for the ne#
database system
-
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%e&uirements Collection and'nalysis
Be9uirements Collection and 5nalysis
he re9uirements speci=cation techni9ues 0information collected at this stage can be
said to be poorly structured and includesome informal re9uests and can beconverted into a more structured statementof re9uirements by using this techni9ue+
FGample: Data Ilo# Diagrams (DID),"ierarchical *nput rocess utput ("*)charts supported by documentation+Computer 5ided Soft#are Fngineering(C5SF) tools, and 7ni=ed ModelingLanguage (7ML)+ -'
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%e&uirements Collection and'nalysis
Main approaches to managing the re9uirements ofdatabase system #ith multiple user vie#+
Centrali>ed 5pproach 0 Be9uirements for eachuser vie# are merged into a single set ofre9uirements for the ne# database system+ 5data model representing all user vie#s iscreated during the database design stage+
Hie# integration 5pproach 0 Be9uirements for
each user vie# remain as separate lists+ Datamodels representing each user vie# are createdand then merged later during the databasedesign stage+
5 combination of both approaches
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Database Desi#n
he process of creating a design that #illsupport the enterprise@s mission statementand mission ob;ectives for the re9uired
database system+ 5pproaches to Database Design
!ottom 0 up
begins at the fundamental levels of
attributes (properties of entities andrelationship)
Jormali>ation
5ppropriate for the design of a simpledatabases #ith a relatively small-6
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Database Desi#n
5pproaches to Database Design
op 0 do#n
Starts #ith the development of data model
(Fntity-Belationship (FB) Model)7sed to design compleG database+
Data Modeling
urpose:
5ssists in the understanding of the meaningof the data
Iacilitate communication about theinformation re9uirements
-
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Database Desi#n
hases of Database Design
Conceptual database design
rocess of constructing a model of the data
used in an enterprise, independent in allphysical consideration
Logical Database design
rocess of constructing a model of the dataused in an enterprise based on speci=c data
model, but independent of a particular D!MSand other physical consideration+
hysical database design
rocess of producing a description of theimplementation of the database on the
secondary storage4 -A
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DS Selection
he selection of an appropriate D!MS tosupport the database system+
Selecting the D!MS:
De=ne terms of reference of study
Shortlist t#o or three products
Fvaluate products
-?
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'pplication Desi#n
he design of the user interface and theapplication programs that use and processthe database+
bserve that the database and applicationdesign are parallel activities of the databasedevelopment lifecycle+ *n most cases, it isnot possible to complete the application
design until the design of the database itselfhas ta8en place+ n the other hand, thedatabase eGists to support the applicationand so there must be a Ko# of information
bet#een application design and databasedesi n+ -1
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'pplication Desi#n
5spects of 5pplication design:
ransaction design 0 an action or series ofaction, carried out by a single user or
application program, that accesses or changesthe content of the database+
urpose of transaction design 0 to de=ne anddocument the high level characteristics of thetransactions re9uired on the database,
including:Data to be used by the transaction4
Iunctional characteristics of thetransaction4
utput the transaction4*m ortance to the users
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'pplication Desi#n
7ser *nterface Design uidelines
Meaningful itle 0 he information conveyed bythe title should clearly identify the purpose of
the formreport+ Comprehensible 0 Iamiliar terminology should
be used to convey instructions to the user+
Logical grouping 0 Belated =elds should bepositioned together on the reportform+ he
se9uencing of =elds should be logical andconsistent+
Hisually appealing layout of the formreport 0the formreport should present an attractiveinterface to the user+
Iamiliar =elds labels 0 Iield labels should be-'
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'pplication Desi#n
7ser *nterface Design uidelines
Consistent terminology and abbreviation 0 anagreed list of familiar terms and abbreviations
should be used consistently+ Consistent use of color 0 color should be used
to improve the appearance of a reportformand to highlight important =elds or importantmessages+
Hisible space and boundaries for data entry=elds 0 a user should be visually a#are of thetotal amount of space available for each =elds+
Convenient cursor movement 0 a user should
easily identify the operation re9uired to movea cursor throu hout the form+
-''
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'pplication Desi#n
7ser *nterface Design uidelines
Frror correction for individual characters andentire =elds 0 user should easily identify the
operation re9uired to ma8e alterations =eldvalues+
Frror message for unacceptable values 0 if auser attempts to enter incorrect data into a=elds, an error message should be displayed+
ptional =elds mar8ed clearly
FGplanatory message for the =elds+
Completion signal
-'3
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"rototypin#
!uilding a #or8ing model of the database system+
5 #or8ing model that does not normally have allthe re9uired features or provide all the
functionality of the =nal system+ rototyping strategies:
Be9uirements prototyping - uses a prototype todetermine the re9uirements of a proposeddatabase system, and once the re9uirements
are complete, the prototype is disregarded+ Fvolutionary prototyping 0 used for the same
purpose, but the diEerence is that the prototypeis not discarded, use #ith further developmentbecomes the #or8ing database system+
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Implementation
he physical reali>ation of the database andapplication designs+
Database implementation is achieved using the DDL
of the selected D!MS or 7*+ 5pplication program are implemented using the
preferred third to fourth generation language (3L or6L)+ arts of these application program are thedatabase transaction, #hich are implemented using
the DML of the target D!MS, possibly embedded#ithin a host programming language such as H!+Jet,ython, Delphi, C, CNN, CO,")+
-'
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Data Conversion and Loadin#
ransferring any eGisting data into thene# database and converting anyeGisting application to run on the ne#
database+
his stage re9uired only #hen a ne#database is replacing an old system+
-'A
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!estin#
he process of running the databasesystem #ith the intent of =ndingerrors+
esting cannot sho# the absence offaults4 it can sho# only that soft#arefaults are present+
Should also cover the usability of thedatabase system+
-'?
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!estin#
Fvaluation sample criteria:
Learnability: "o# long does it ta8e a ne#user to become productive #ith the
systemPerformance: "o# #ell does the system
response match the user@s #or8 practiceP
Bobustness: "o# tolerant is the system of
user errorPBecoverability: "o# good is the system
from recovering from user errorsP
5daptability: "o# closely is the system
tied to a single model of #or8P -'1
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Operational aintenance
he process of monitoring and maintaining the databasesystem follo#ing installation+
5ctivities involve:
Monitoring the performance of the system+ *f the
performance falls belo# an acceptable level, tuningor reorgani>ation of the database may be re9uired+
Maintaining and upgrading the database system(#hen re9uired)+ Je# re9uirements are incorporatedinto the database system through the preceding
stages of the lifecycle+
nce the database is fully operational, closemonitoring ta8es place to ensure that performanceremains #ithin acceptable levels+
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FGercise :
5ssume that you are an employeeconsultancy company that speciali>es in theanalysis, design and implementation ofdatabase systems+ 5 client has recentlyapproach your company #ith a vie# toimplementing a database system but theyare not familiar #ith the development
process+ Qou have been assigned the tas8 topresent an overvie# of the database systemdevelopment Lifecycle (SDLC) to them,identifying the main stages of this lifecycle+
Rith this tas8 in mind create a slide-3
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he Client
5ppendiG !: he #ellmeado#s"ospital Case study+
-3
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FGercise ':
*ntervie# one or more people responsible for thedevelopment andor administration of a real databasesystem+ During the intervie# =nd out the follo#ing
information:a+ he approach ta8en to develop the database
system+
b+ "o# the approach ta8en diEers or similar to theDSDL approach described in this chapter+
c+ "o# the re9uirements for diEerent users(user vie#)of the database system #ere managed+
d+ "o# the D!MS product #as evaluated and thenselected+
e+ "o# the database system is monitored and
maintained 3'
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