DFD Symbology

DeMarco-YourdonSymbology

Gane-SarsonSymbology

Examples

Process

Data Store

Entity

Data Flow

6.1

CreateEmployee

PayrollCheck

Customer

New Customer Information

InventoryFile

D7

DFD for Peeling an Apple

1.0

GetApple

AppleStorageS1

Peeling DeviceStorageS2

2.0

GetPeelingDevice

4.0

HoldApple

3.0

WashApple

6.0

DiscardPeel

5.0

Peel AppleWith

Peeling Device

7.0

Send PeeledApple

ToProcessor

PeelDisposalS2

ProcessedApple

System

Unwashed Apple

Unwashed Apple

Washed Apple Washed Apple

Peeling Device

Peeling Device Apple Peel

Apple Peel

Peeled ApplePeeled Apple

Context-Level Diagram

0

EmployeePayrollSystem

Employee Tax Form

Payroll Report

Time Sheet

Employee Payroll Check

Employee

Accounting Department

Level-0 DFD

1.0

CreateWeeklyPayrollRecord

Employee Data File

S1Employee Payroll Data File

S2

2.0

ComputeWeekly

Paycheck

3.0

PrepareWeeklyPayroll

Summary

4.0

PrepareEmployee

TaxForm

AccountingDepartment

Employee Record Paycheck Data

Payroll Record

Payroll Report

Employee Paycheck

Employee Tax Form

Time Sheet

Hours Worked

Employee Payroll Record

Level-1 DFD

1.0

CreateWeeklyPayrollRecord

Employee Data FileS1

Employee Tax Form

Payroll Data FileS2

2.1

ComputeGross

Pay

2.3

CreatePayrollCheck

2.2

ComputeNetPay

3.2

PrintWeeklyPayroll

Summary

3.1

SortPayroll

Records byEmployee

4.2

PrintEmployee

TaxForm

4.1

CalculatePayroll

Deductions

Employee Paycheck

PayrollDeductions

Employee PayrollRecord

Time Sheet

Employee Record

Gross PayData

Net PayData

Hours Worked

Payroll Record

Sorted Records

Payroll Report

Employee

Accounting Department

Partial Level-n DFD

4.1.2

CalculateNon-tax

Deductions

4.1.3

CalculateRetirementAllowance

4.2.1

CalculateEmployeeVacation

Pay

4.1.1

CalculatePayroll

TaxDeductions

4.2.2

PrintEmployeeTax Form

EmployeeData

EmployeeData

EmployeeData

Employee Tax Form

EmployeePayrollRecord

Employee Data

Rules Governing DFD Construction

• A process cannot have only outputs – “Miracle.”• A process cannot have only inputs – “Black Hole.”• The inputs to a process must be sufficient to produce the outputs from the

process - (Gray Hole).• All data stores must be connected to at least one process.• A data store cannot be connected to a source or sink. • A data flow can have only one direction of flow. Multiple data flows to and/or

from the same process and data store must be shown by separate arrows. • If the exact same data flows to two separate processes, it should be

represented by a forked arrow. • Data cannot flow directly back into the process it has just left. • All data flows must be named using a noun phrase.

ANSI Flowchart Symbology

Program

LibraryProgram

ManualOper.

Punch Card

SourceDocument

MultipleDocuments

TapeFile

Disk File

Database

Sort

Extract

MergeDecisio

nTermination

System Flowchart

Order-EntryDept.

MemberOrders

InputMemberOrders

MemberOrders

Member OrderEdit

ProgramValid

Orders

Sort by #

SortedMember Orders

Member Order Error

Report

Correct

OrderErrors

Functional Primitive

4.1.2

CalculateNon-tax

Deductions

4.1.3

CalculateRetirementAllowance

4.2.1

CalculateEmployeeVacation

Pay

4.1.1

CalculatePayroll

TaxDeductions

4.2.2

PrintEmployeeTax Form

EmployeeData

EmployeeData

EmployeeData

Employee Tax Form

EmployeePayrollRecord

Employee Data

Non-Probabilistic Decision Tree

ProcessName

Condition 1 (true)

Condition 2 (false)

Condition 1 (false)

Condition 2 (true)

Condition 2 (false)

Condition 2 (true)

1

2

2

Action 1

Action 2

Action 3

Action 4

Decision Tree Example

SurchargeRating

< 25 yrs.

No

25 yrs. +

Yes

1

2

2

10%

20%

7%

0%Yes

3

4

5

6

F

M15%

12%

10%

7%

No

Yes No

Yes< 3.25

3.25+

DriverAge

AccidentFree

DriverGender

Driver’sEduc.

CollegeEduc.

H.S.GPA

Surcharge

State-Transition Diagram

State

TransitionErrorState

2. OperatingState

1. IdleState

S5. MajorError

Cleared

S1. ON buttonPushed

S3. ErrorConditionDetected

S2. OFF buttonpushed

S4. MinorError

Cleared

Problem 1 DFD

1.0 2.0

3.0

Insurance Claimant

Insurance Claimant

Claims ManagerClaims

Manager

Home OfficeHome Office

Claims File

Verify Claim

Review Client

History

Issue Claim

Payment

InsuranceClaim

InsuranceClaim

Claim Payment

Amount Paid

Monthly ClaimsAnalysis

ClaimsReport

Structured English for Process 4.x

Process ID

Structured English

4.1.1 

Multiply GROSS_PAY by FED_TAX_RATE and store in EMP_TAX_DEDUCT.

4.1.2 

IF EMP_NONTAX_DEDUCT > 0 THEN append EMP_NONTAX_DEDUCT to employee data. 

4.1.3 

Multiply GROSS_PAY by .01 and store in EMP_RETIRE.

4.1.4 

Multiply CURR_EMP_VACATION by EMP_DAY_RATE and store in EMP_VACATION_PAY.