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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.

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Presentation on theme: "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."— Presentation transcript:

1 DFD examples

2 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

3 1.External entities … noun 2.Data flows.. Name of data 3.Process..verb phrase ( system name, sub sytem name) 4.Data store..noun

4 (draw your context diagram)

5 Level-0 DFD

6 2.0 P1 1.0 P2 E1 E2 DF1 DF3DF6 DF5 DF2 DF4 DS1 Consider the following DFD. List two errors on this DFD

7 Logizian Analyst edition

8 Ordering a tuna roll

9 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. Tuna roll please! Ordering some lunch

10 The waitresses Order 1 x Tuna roll The waitresses write this down and passes the order to the chef. Order 1 x Tuna roll Ordering some lunch

11 The chef Order 1 x Tuna roll The chef gets the order and makes the roll. The roll is then passed back to the waitress. Ordering some lunch

12 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 roll RM 2.99 Thank you Ordering some lunch

13 The waitresses The customer When the food arrives from the chef, the waitress gives it to the customer. Ordering some lunch

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

15 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

16 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.

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19 DFD Symbols External Entity Flow of Data Process Data Store Customer Bill Preparing a bill Menu Chef

20 The customer is a source of information – the person who start the whole process off. The chef is a destination of the information. Customer Chef

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

22 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! Customer Chef Order sandwich

23 Sandwich prices 1. order 2. order 5. invoice 6. payment 7. receipt 3. query price4. price Customer Chef Order sandwich 8. Tuna 9. Tuna

24 Before you start! A few rules to follow!!

25 Customer Chef

26 Order sandwich Customer Sandwich prices Chef


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