Creating Data Flow Diagrams Presenter: Ms. Somia Razzaq

Creating Data Flow Diagrams

Presenter: Ms. Somia Razzaq

Data Flow Diagrams Symbols

Source/ Sink

0.0Process

DATA STORE

Data Flow Lines

DeMarco & Yourdon

Logical Data Flow Diagrams – show the data flow, structure, and requirements of a new system

Physical Data Flow Diagrams – show how the current system flows

System Analysis and Design

System – a group of interrelated procedures used for a business function, with an identifiable boundary, working together for some purpose.

Analysis – separation of a whole into its component parts

Design – to create, fashion, execute, or construct according to plan


Source/ Sink

0.0Process

DATA STORE

Data Flow Lines

DeMarco & Yourdon

Source/Sink – help to establish the boundaries of the system. A source identifies the origin of data inflow to the system. A sink identifies the outflow of a system, many times as information.

Sometimes referred to an entity, a source may be a customer, vendor, employee, or even another system. A single entity can be both a source and a sink.


Source/ Sink

0.0Process

DATA STORE

Data Flow Lines

DeMarco & Yourdon

Processes – are the activities (manual and automated) that transform the inputs, transport data from process to process, stores the data, and produce the outputs of a system.

Processes are used on every DFD starting with an over all process on the context level diagram, the system. The system is then decomposed until a primitive level is obtained. The primitive level is the point in which the relevant activities of a process are identified.


Source/ Sink

0.0Process

DATA STORE

Data Flow Lines

DeMarco & Yourdon

Data Store – is the resting place of the data in a system. A data store can be in the form of paper, a disk file or any other media.

Normally the word ‘data’ does not appear in the title of a data store. Some examples of data stores are Customer Order, Payment, Invoice, Time Card……


Source/ Sink

0.0Process

DATA STORE

Data Flow Lines

DeMarco & Yourdon

Data Flow – is the data in motion. Data can move from the outside (source) into a process. Once the inside of a system data must flow from place to place through a process, the flow lines show this movement.

The lines are labeled to provide clarity and meaning to the data moving through the system.

Data Flow Diagrams Levels

Source/ Sink

0.0Process

DATA STORE

Data Flow Lines

DeMarco & Yourdon

0.0Process Source/ SinkSource/ Sink

Data FlowData Flow

Data Flow

2.0ProcessData Flow

Source/ SinkSource/ SinkData Flow

1.0Process

3.0Process

Data Flow

Data Flow

Data FlowData Flow

Data Flow

Context Level DFD

Level 0 DFD

Data Flow Diagrams Levels

Source/ Sink

0.0Process

DATA STORE

Data Flow Lines

DeMarco & Yourdon

1.2Process

1.1Process

Data Flow

Data Flow

DATA STORE

Data Flow

Level 1 DFD (and on)Source

Source

Sink

Prepared by: yourname

Date: 01/01/2002

Level 1 DFD

Project Name

1.2Process

1.1Process

Data Flow

Data Flow

DATA STORE

Data Flow


Date: 01/01/2002

Level 1 DFD

Project Name

2.2Process

2.1Process

Data Flow

Data Flow

DATA STORE

Data Flow


Date: 01/01/2002

Level 1 DFD

Project Name

3.2Process

3.1Process

Data Flow

Data Flow

DATA STORE

Data Flow

Data Flow Diagrams LevelsPrepared by: yourname

Date: 01/01/2002

Context Level DFD

Project Name

0.0Process Source/ SinkSource/ Sink

Data FlowData Flow

Data Flow


Date: 01/01/2002

Level 0 DFD

Project Name

2.0ProcessData Flow

Source/ SinkSource/ SinkData Flow

1.0Process

3.0Process

Data Flow

Data Flow

Data FlowData Flow

Data Flow


Steps:

1. Create a list of activities

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

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

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


Lemonade Stand Example


Steps:



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


Example

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


1. Create a list of activitiesExample

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

Customer OrderServe ProductCollect PaymentProduce ProductStore Product


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 Labor



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 Labor



0.0Lemonade

SystemEMPLOYEECUSTOMER

PayPayment

Order

Context Level DFD

Example

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




Pay for Labor

VENDOR

PaymentPurchase Order

Production Schedule

Received GoodsTime Worked

Sales Forecast


Product Served


Level 0 DFD

Example

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




Pay for Labor

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

VENDOR

Payment

Purchase Order Order Decisions

Received Goods

Time Worked

Inventory

Product Served

4.0Payroll


Level 1 DFD

Example

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


1.3Produce

Sales Forecast Sales ForecastPayment




Pay for Labor

1.1Record Order

Customer Order

ORDER

1.2Receive Payment

PAYMENT

Severed Order

Request for Forecast

CUSTOMER


Level 1 DFD

Example


4. Construct Level 1 (continued)




Pay for Labor

2.1Serve

Product

Product Order

ORDER

2.2Produce Product

INVENTORTY

Quantity Severed

Production Schedule

RAW MATERIALS

2.3Store

Product

Quantity Produced & Location Stored

Quantity Used

Production Data


Level 1 DFD

Example






Pay for Labor

3.1Produce Purchase

Order

Order DecisionPURCHASE

ORDER

3.2Receive

Items

Received Goods

RAW MATERIALS

3.3Pay

Vendor

Quantity Received

Quantity On-Hand

RECEIVED ITEMS

VENDOR

Payment Approval

Payment


Level 1 DFD

Example



Time Worked




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 Decomposition

4.1Record Time

Worked

4.2Calculate

Payroll

4.3Pay

Employee

3.1Produce Purchase

Order

3.2Receive

Items

3.3Pay

Vendor

2.1Serve

Product

2.2Produce Product

2.3Store

Product

1.1Record Order

1.2Receive Payment

2.0Production

1.0Sale

3.0Procure-

ment

4.0Payroll

0.0Lemonade

System

Level 0 Level 1Context Level


Lemonade Stand Example

END

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Creating Data Flow Diagrams Presenter: Ms. Somia Razzaq