DFD Examples

Computer Dynamics

Creating Data Flow Diagrams

Steps:

1. Create a list of activities

2. Construct Context Level DFD(identifies external entities and processes)

3. Construct Level 0 DFD (identifies manageable sub process )

4. Construct Level 1- n DFD (identifies actual data flows and data stores )

5. Check against rules of DFD

DFD Naming Guidelines

• External Entity Noun

• Data Flow Names of data

• Process verb phrase

– a system name

– a subsystem name

• Data Store Noun

Creating Data Flow Diagrams

Lemonade Stand Example

Creating Data Flow Diagrams

Steps:

1. Create a list of activities

• Old way: no Use-Case Diagram

• New way: use Use-Case Diagram

2. Construct Context Level DFD(identifies sources and sink)

3. Construct Level 0 DFD (identifies manageable sub processes )

4. Construct Level 1- n DFD (identifies actual data flows and data stores )

Example

The operations of a simple lemonade stand will be used to demonstrate the creation of dataflow diagrams.

Creating Data Flow Diagrams

1. Create a list of activitiesExample

Think through the activities that take place at a lemonade stand.

Customer OrderServe ProductCollect PaymentProduce ProductStore Product

Creating Data Flow Diagrams

Example

Also think of the additional activities needed to support the basic activities.

Customer OrderServe ProductCollect PaymentProduce ProductStore ProductOrder Raw MaterialsPay for Raw MaterialsPay for Labour

1. Create a list of activities

Creating Data Flow Diagrams

Example

Group these activities in some logical fashion, possibly functional areas.

Customer OrderServe ProductCollect Payment

Produce ProductStore Product

Order Raw MaterialsPay for Raw Materials

Pay for Labour

1. Create a list of activities

Creating Data Flow Diagrams

0.0Lemonade

SystemEMPLOYEECUSTOMER

Pay

Payment

Order

Context Level DFD

Example

Create a context level diagram identifying the sources and sinks (users).

Customer OrderServe ProductCollect Payment

Produce ProductStore Product

Order Raw MaterialsPay for Raw Materials

Pay for Labour

SUPPLIER

PaymentPurchase Order

Production Schedule

Received GoodsTime Worked

Sales Forecast

2. Construct Context Level DFD(identifies sources and sink)

Product Served

Creating Data Flow Diagrams

Level 0 DFD

Example

Create a level 0 diagram identifying the logical subsystems that may exist.

Customer OrderServe ProductCollect Payment

Produce ProductStore Product

Order Raw MaterialsPay for Raw Materials

Pay for Labour

3. Construct Level 0 DFD (identifies manageable sub processes )

2.0Production EMPLOYEEProduction

Schedule

1.0Sale

3.0Procure-

ment

Sales Forecast

Product Ordered

CUSTOMER

Pay

Payment

Customer Order

SUPPLIER

Payment

Purchase Order Order Decisions

Received Goods

Time Worked

Inventory

Product Served

4.0Payroll

Creating Data Flow Diagrams

Level 1 DFD

Example

Create a level 1 decomposing the processes in level 0 and identifying data stores.

4. Construct Level 1- n DFD (identifies actual data flows and data stores )

1.3Produce

Sales Forecast

Sales ForecastPayment

Customer OrderServe ProductCollect Payment

Produce ProductStore Product

Order Raw MaterialsPay for Raw Materials

Pay for Labor

1.1Record Order

Customer Order

ORDER

1.2Receive Payment

PAYMENT

Serve Order

Request for Forecast

CUSTOMER

Creating Data Flow Diagrams

Level 1 DFD

Example

Create a level 1 decomposing the processes in level 0 and identifying data stores.

4. Construct Level 1 (continued)

Customer OrderServe ProductCollect Payment

Produce ProductStore Product

Order Raw MaterialsPay for Raw Materials

Pay for Labor

2.1Serve

Product

Product Order

ORDER

2.2Produce Product

INVENTORY

Quantity Served

Production Schedule

RAW MATERIALS

2.3Store

Product

Quantity Produced & Location Stored

Quantity Used

Production Data

Creating Data Flow Diagrams

Level 1 DFD

Example

Create a level 1 decomposing the processes in level 0 and identifying data stores.

4. Construct Level 1 (continued)

Customer OrderServe ProductCollect Payment

Produce ProductStore Product

Order Raw MaterialsPay for Raw Materials

Pay for Labor

3.1Produce Purchase

Order

Order DecisionPURCHASE

ORDER

3.2Receive

Items

Received Goods

RAW MATERIALS

3.3Pay

Supplier

Quantity Received

Quantity On-Hand

RECEIVED ITEMS

SUPPLIER

Payment Approval

Payment

Creating Data Flow Diagrams

Level 1 DFD

Example

Create a level 1 decomposing the processes in level 0 and identifying data stores.

4. Construct Level 1 (continued)

Time Worked

Customer OrderServe ProductCollect Payment

Produce ProductStore Product

Order Raw MaterialsPay for Raw Materials

Pay for Labor

4.1Record Time

Worked

TIME CARDS

4.2Calculate

Payroll

Payroll Request

EMPLOYEE

4.3Pay

Employee

Employee ID

PAYROLL

PAYMENTS

Payment Approval

Payment

Unpaid time cards

Process Breakdown

4.1Record Time

Worked

4.2Calculate

Payroll

4.3Pay

Employee

3.1Produce Purchase

Order

3.2Receive

Items

3.3Pay

Supplier

2.1Serve

Product

2.2Produce Product

2.3Store

Product

1.1Record Order

1.2Receive Payment

2.0Production

1.0Sale

3.0Procurement

4.0Payroll

0.0Lemonade

System

Level 0 Level 1Context Level

DFD Example: Bus Garage Repairs

• Buses come to a garage for repairs. • A mechanic and helper perform the repair,

record the reason for the repair and record the total cost of all parts used on a Shop Repair Order.

• Information on labour, parts and repair outcome is used for billing by the Accounting Department, parts monitoring by the inventory management computer system and a performance review by the supervisor.

DFD Example: Bus Garage Repairs (cont’d)

• External Entities: Bus, Mechanic, Helper, Supervisor, Inventory Management System, Accounting Department, etc.

• Key process (“the system”): performing repairs and storing information related to repairs

• Processes: – Record Bus ID and reason for repair– Determine parts needed– Perform repair– Calculate parts extended and total cost– Record labor hours, cost

DFD Example: Bus Garage Repairs (cont’d)

• Data stores: – Personnel file– Repairs file– Bus master list– Parts list

• Data flows:– Repair order– Bus record– Parts record– Employee timecard– Invoices

Bus

Mechanic

Helper Bus Repair ProcessSystem

Supervisor

Accounting

Bus Garage Context Diagram

Mechanical problem to be repaired

Labour

Labour

Fixed mechanical problems

Inventory Management

System

Repair summary

List of parts used

Labour, parts cost details

CSUB Burger’s Order Processing System

• Draw the CSUB Burger’s context diagram– System

• Order processing system

– External entities• Kitchen• Restaurant• Customer

– Processes• Customer order• Receipt• Food order• Management report