dfd examples. steps 1.create a list of activities 2.construct context level dfd (identifies external...
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DFD examples
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
1. External entities … noun2. Data flows .. Name of data3. Process ..verb phrase ( system name , sub
sytem name)4. Data store ..noun
(draw your context diagram)
ACCOUNTING
WAREHOUSECUSTOMER
0
Order System
Order
Payment
In-StockRequest
StatusMessage
Invoice Shipping Confirmation
Shipping Order
Inventory Reports
Level-0 DFD
1.0
CheckStatus
2.0
IssueStatus
Messages
3.0
GenerateShipping
Order
ACCOUNTING
CUSTOMER WAREHOUSE
4.0
Manage Accounts
Receivable5.0
ProduceReports
Order In-Stock Request
Status Data
Status Message
PendingOrdersD1
Order Data
Order Data
Shipping Order
Shipping Confirmation
Invoice
Payment
Accounts ReceivableD2
Accounting Data Accounts Receivable Data
Order Data
Inventory Reports
2.0
P1
P1
1.0
P2
P2
E1
E1
E2
E2
DF1
DF3DF6
DF5
DF2
DF2
DF4
DS1
Consider the following DFD. List two errors on this DFD
• Logizian Analyst edition• http://www.visual-paradigm.com/product/lz/tutorials/dfd.jsp
Ordering a tuna roll
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 flow
The next few slides demonstrate how to produce the data flow diagram – this example is for ordering a tuna 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 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!
A few rules to follow!!
CustomerCustomer ChefChef
Order sandwich
CustomerCustomer
Sandwich prices
ChefChef