chapter3 dsdlc

8/17/2019 Chapter3 DSDLC

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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+

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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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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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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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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


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


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

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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+

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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+

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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'

chapter3 dsdlc

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