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8/9/2019 DFD diagram
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Process Models:Process Models:
Data Flow DiagramsData Flow DiagramsSpecial thanks goes to Dr. Jack T. Marchewka for many of the ideas
and examples contained in these notes.
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Process Modeling Objective:
Understand the concept of business
processes Understand and create Data Flow
Diagrams.
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DFDs
Visuall represent data !ows
processes
"mphasi#e the logic of sstem
Provide documentation for $nalsis% Design
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Data Flow Diagrams
Data Flow
Process
File or Data Store
Source or Entity
Gane & Sarson Methodology
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DFDs
Do not show technical aspects &how interrelations of sstems %
subsstems Facilitates
developer understanding
user'developer communication (ompleteness of data % process
de)nitions
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*he &stems (oncept
Input Process Output
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DFDs
1
Process
Data Flow
Input
Data Flow
Output
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Developing DFDs
(onte+t Diagram &stem Overview
,ittle or no detail
-ero ,evel "+plosion More detailed
First&econd *hird ,evels More detailed levels
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(onte+t DFD
/asic overview of the sstem
(ontains onl 0 process given the number #ero
&hows all e+ternal entities
Major data !ows among entities
1enerall no data stores
$ssign a name to the whole sstem
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(onte+t DFD "+amples
!partment
"ental
System
#enant
$an%
Eternal
Manager'ease(
Payments
$an% Deposit
'ease
)ash"eport
"eceipts( *otices
$partment 2ental
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2ecall: on'line universitregistration 3from Use (ase
e+amples4
*he sstem should enable the sta5 of each academicdepartment to e+amine the course o5ered b their
department add and remove course and change theinformation about them 3e.g. the ma+imum number ofstudents4. 6t should permit students to e+amine currentlavailable courses add and drop courses to and from theirschedules and e+amine the course for which the areenrolled. Department sta5 should be able to print a variet ofreports about the courses and the students enrolled in them.*he sstem should ensure that no student ta7es too mancourse and that students who have an unpaid fees are notpermitted to register. 3$ssume that a fees data store ismaintained b the universit8s )nancial o9ce that the
registration sstem accesses but does not change.4
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Department
Sta++
)ourse
"egistration
System
)ourse
in+ormation
)ourseo++erings
Enrollment
in+ormation
StudentsStudentschedules
2egistration (onte+t Diagram
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2ecall: real estate 3from Use (asee+amples4
$ 2eal "state 6nc. 3$2"64 sells houses. People who want to selltheir houses sign a contract with $2"6 and provide informationon their house. *his information is 7ept in a database b $2"6
and a subset of this information is sent to the citwide multiple'listing service used b all real estate agents. $2"6 wor7s withtwo tpes of potential buers. &ome buers have an interest inone speci)c house. 6n this case $2"6 prints information from itsdatabase which the real estate agent uses to help show the
house to the buer 3a process beond the scope of the sstem tobe modeled4. Other buers see7 $2"6s advice in )nding a housethat meets their needs. 6n this case the buer completes abuer information form that is entered into a buer databaseand $2"6 real estate agents use its information to search $2"6sdatabase and the multiple'listing service for houses that meet
their needs. *he results of these searches are printed and used
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Sellers
!"EI
System
,ouse
in+ormation
$uyer
in+ormation
,ouse
In+ormation
$uyers,ouse
in+ormation
,ouse
In+ormation
Multiple
'isting
Ser-ice
$2"6 (onte+t Diagram
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,evel ; DFD
Detail from
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1
.
/
#enant
*ew
#enant
Process
)ollection
Process
Delin0uent
Process
'ease
D1 #enant File#enant In+o'e-el DFD: !partment "ental
Payments
$an%$an%
Deposit
"eceipt
Et
Mgr
)ash "eport
D1 #enant File
2npaid)harges
Delin0uency"eport
#enant
In+o
Delin0uencies
)opy o+ lease
*otice
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'e-el DFD: "egistration
Dept
Sta++
1
Maintain
department
course
o++erings
.
Maintain
student
enrollments
/
)ourse
Enrollment
"eports
)ourse O++ering
)hanges
)ourse
O++erings
!-aila3le
courses
D1 Fees
D. )ourse O++erings
D/ Enrollments)ourse
in+ormation
Student Enrollment
"eport "e0uest
Student
Enrollment
"eport
Enrollment
in+ormation
Students
)ourse
O++ering
2pdates
)ourse O++ering
'ist
Fee Payment
,istory
!-aila3le
course re0uest
!-aila3le courses
!-aila3le
courses
)ourse enrollment
Student schedule
Student
schedule
)ourse
enrollment
re0uest
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'e-el DFD: !"EI
Sellers
Maintain
house
seller
information
D2 Sales Contracts
House
information
Generate
requested
report
1
2
Sales Contract
D3 Offered Houses
House information
Buyer information form
D1
Multiple Listin
Ser!ices "ile
House information
Sales
Contract
House information
House information
House information
Buyers
House information request
D# Buyers
Buyer
information
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(reate (hild Diagrams
Vertical /alancing $ child diagram cannot produce
output or receive input that theparent does not produce or receive
"+ternal entities are not shown
Ma contain additional data stores e.g.. transaction )les Primitive when no longer e+ploded
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Deposit )hec%s
"ent )hec%s
.1
..
)ollect
SecurityDeposit
)ollect
"ent
Deposit "eceipts
Payment "eceipts
2npaid
)harges
$an% Deposit
$an% Deposit
D1 #enant File
#enant
In+o
#enantIn+o
)ash
"eport
'e-el 1 DFD: !partment "ental
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Deposit
)hec%
.11
Ma%e
$an%Deposit
$an%
Deposit
.1.2pdate
#enant
File
Deposit
In+o
D1 #enant File2pdate
In+o
.1/
)reate
"eceipt
#enant
In+o
"eceipt
'e-el . DFD: !partment "ental
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'e-el 1 DFD 41 o+ /5: "egistration
Dept
Sta++
Produce
course
o++ering
list
!dd new
course
Department ID
Department ID
D. )ourse O++erings
)ourse to
delete
)ourse modi+ications
)ourse O++ering
'ist "e0uest
)ourse o++ering list
*ew )ourse
in+ormation
*ew )ourse
Delete
course
Modi+y
eisting
courses
)ourse to delete
)ourse modi+ications
Eisting )ourse
in+ormation
11
1.
1/
16
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'e-el 1 DFD 4. o+ /5: "egistration
Students
Produce
course
o++ering
list
!dd course
to schedule
D. )ourse O++erings
)ourse to
delete
)urrent schedule re0uest
!-aila3le courses
)ourse to add
to enrollment
)ourse enrollment add
Delete
course +rom
schedule
O3tain
current
schedule
)ourse to delete
.1
..
./
.6
!-aila3le )ourse
"e0uest
!-aila3le
)ourses
D/ Enrollments
D1 Fees
Student enrollment
in+ormation
Fee payment history
)ourse enrollment
add
Student schedule
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'e-el 1 DFD 4/ o+ /5: "egistration
Dept
Sta++
O3tain
report
type
D. )ourse O++erings
"eport
type
)ourse o++ering
in+ormation
Generate
re0uested
report
/1
/.
"eport
"e0uest
D/ EnrollmentsEnrollment
in+ormation"e0uested
report
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(ommon "rrors
Forgetting data !ows
$rrow pointing wrong wa
(onnecting data stores % sources
6ncorrectl labeling processes or !ows
*oo man processes 3brea7 it up@4
Data !ows entering a process mustbe di5erent when leaving@
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,ogical % Phsical
DFDs ,ogical
focuses on modeling the business
sstem independent
Phsical focuses on modeling the sstem
sstem dependent
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,ogical DFDs ' (urrent&stem
1ood for communication %understanding
Focus on business activities User view of the current sstem
Model of the business
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,ogical DFDs ' ?ew &stem
,oo7 for improvements e5ectiveness ' i.e. doing the
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Phsical DFDs
Use the new logical DFD to ma7e transitionto a (/6&
De)ne Machine versus manual boundaries processes A programs or manual procedures
data stores A data )les or manual )les
De)ne controls validations % securit
De)ne actual )le names % printouts Master % transaction )les
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Partitioning the Phsical
DFD De)ning
manual procedures
automated procedures circled using a dotted line
/atch versus On',ine Procedures
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Deposit
)hec%
.11
Ma%e
$an%Deposit
$an%
Deposit
.1.2pdate
#enant
File
Deposit
In+o
D1 #enant File2pdate
In+o
.1/
)reate
"eceipt
#enant
In+o
"eceipt