DFD diagram

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.


2/31

Process Modeling Objective:

Understand the concept of business

processes Understand and create Data Flow

Diagrams.


3/31

DFDs

Visuall represent data !ows

processes

"mphasi#e the logic of sstem

Provide documentation for $nalsis% Design


4/31

Data Flow Diagrams

Data Flow

Process

File or Data Store

Source or Entity

Gane & Sarson Methodology


5/31

DFDs

Do not show technical aspects &how interrelations of sstems %

subsstems Facilitates

developer understanding

user'developer communication (ompleteness of data % process

de)nitions


6/31

*he &stems (oncept

Input Process Output


7/31

DFDs

1

Process

Data Flow

Input

Data Flow

Output


8/31

Developing DFDs

(onte+t Diagram &stem Overview

,ittle or no detail

-ero ,evel "+plosion More detailed

First&econd *hird ,evels More detailed levels


9/31

(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


10/31

(onte+t DFD "+amples

!partment

"ental

System

#enant

$an%

Eternal

Manager'ease(

Payments

$an% Deposit

'ease

)ash"eport

"eceipts( *otices

$partment 2ental


11/31

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


13/31

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


14/31

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


15/31

,evel ; DFD

Detail from


16/31

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


19/31

(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


20/31

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


23/31

'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


24/31

'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


25/31

(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@


26/31

,ogical % Phsical

DFDs ,ogical

focuses on modeling the business

sstem independent

Phsical focuses on modeling the sstem

sstem dependent


27/31

,ogical DFDs ' (urrent&stem

1ood for communication %understanding

Focus on business activities User view of the current sstem

Model of the business


28/31

,ogical DFDs ' ?ew &stem

,oo7 for improvements e5ectiveness ' i.e. doing the


29/31

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


30/31

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

Documents

DFD diagram