DFD ExamplesDFD Examples

Create a data flow diagramCreate a data flow diagram

Which way does the window faceWhich way does the window face

How many legs do you seeHow many legs do you see

Information flowInformation flow

In this task you will produce a In this task you will produce a simple data flow diagramsimple data flow diagram

Your task is to produceYour task is to produce

► A diagram showing the information flow A diagram showing the information flow when sandwiches are sold, calculations are when sandwiches are sold, calculations are made, there is some sort of output.made, there is some sort of output.

► Details showing the terminators/entities, Details showing the terminators/entities, processes and data stores.processes and data stores.

Ordering a tuna rollOrdering a tuna roll

Information flowInformation flowClick to move through this show.Click to move through this show.

The customerA customer wants to order some lunch. They walk to the counter and ask for the menu. They make their choice and ask the waitress for a tuna roll.

Tuna roll please!

Ordering some lunch

The waitresses

The waitresses write this down and passes the order to the chef.

Order1 x Tuna roll

Ordering some lunch

The chef

Order1 x Tuna roll

The chef gets the order and makes the roll. The roll is then passed back to the waitress.

Ordering some lunch

The waitresses

The customer

Whilst the chef makes the roll, the waitress gives the customer a paper bill produced from the cash till. This shows how much the customer owes.

The customer pays their bill.

Coffee Control

1 tuna rollRM 2.99

Thank you

Ordering some lunch

The waitresses

The customer

When the food arrives from the chef, the waitress gives it to the customer.

Ordering some lunch

Information flowInformation flow

The next few slides demonstrate how The next few slides demonstrate how to produce the data flow diagram – to produce the data flow diagram – this example is for ordering a tuna this example is for ordering a tuna roll.roll.

1.Put a square around any inputs or outputs involved - these are entities.

2.Circle any data stores. 3.Underline any processing that takes

place 4.Sketch out the information flow, joining

up the people (entities, the processing and the data stores

Analyse the problem

A customer wants to order some lunch. They walk to the counter and ask for the menu. They make their choice and ask the waitress for a tuna roll. The waitresses write this down and passes the order to the chef. The chef gets the order and makes the roll. The roll is then passed back to the waitress. Whilst the chef makes the roll, the waitress gives the customer a paper bill produced from the till. This shows how much the customer owes. The customer pays their bill. When the food arrives from the chef, the waitress gives it to the customer.

A customer wants to order some lunch. They walk to the counter and ask for the menu. They make their choice and ask the waitress for a tuna roll. The waitresses write this down and passes the order to the chef. The chef gets the order and makes the roll. The roll is then passed back to the waitress. Whilst the chef makes the roll, the waitress gives the customer a paper bill produced from the till. This shows how much the customer owes. The customer pays their bill. When the food arrives from the chef, the waitress gives it to the customer.

A customer wants to order some lunch. They walk to the counter and ask for the menu. They make their choice and ask the waitress for a tuna roll. The waitresses write this down and passes the order to the chef. The chef gets the order and makes the roll. The roll is then passed back to the waitress. Whilst the chef makes the roll, the waitress gives the customer a paper bill produced from the till. This shows how much the customer owes. The customer pays their bill. When the food arrives from the chef, the waitress gives it to the customer.

DFD SymbolsDFD Symbols

External Entity

Flow of Data

Process

Data Store

Customer

Bill

Preparing a bill

Menu

Chef

The customer is a source of information – the person who start the whole process off.

The chef is a destination of the information.

CustomerCustomer ChefChef

Sandwich prices

The menu or price list keeps a record of prices – it is a data store.

CustomerCustomer ChefChef

Sandwich prices

The waitress processes the order

The waitress is not shown as an entity because she does not produce or receive information (ultimately – the order goes to the chef!!). She is not a data SOURCE or SINK!

CustomerCustomer ChefChefOrder sandwich

Sandwich prices

1. order

2. order5. invoice

6. payment

7. receipt

3. query price4. price

CustomerCustomer

ChefChefOrder sandwich

8. Tuna

9. Tuna

Before you start!Before you start!

A few rules to follow!!A few rules to follow!!

CustomerCustomer ChefChef

Order sandwich

CustomerCustomer

Sandwich prices

ChefChef

Assignment – CDs by mail Assignment – CDs by mail orderorder

Bebop Records is a mail-order company that distributes CDs and tapes at discount prices to record club members. When anorder processing clerk receives an order formorder form, he or she verifies thatthe sender is a club member by checking the Member file. If thesender is not a member, the clerk returns the orderthe order along with amembership application formmembership application form. If the customer is a member, theclerk verifies the order itemverifies the order item data by checking the Item file. Thenthe clerk enters the order data and saves it to the Daily Order file.The clerk also prints an invoice and shipping listinvoice and shipping list for each order,which are forwarded to Order Fulfillment.

Annotating the textAnnotating the textProcessingProcessing

Annotating the textAnnotating the textData storesData stores

Annotating the textAnnotating the textEntitiesEntities

The endThe end

DFDsDFDs