1. System Analysis and Design
Data Flow Diagram

2. Data Flow diagram
The dataflow diagram is a modeling tool that allows us to picture a system as a network of functional processes, connected to one another by “pipelines” and “holding tanks” of data

3. Data Flow Diagrams Context Diagrams
Top-level view of an information system that shows the system’s boundaries and scope
Do not show any data stores in a context diagram because data stores are internal to the system.
Begin by reviewing the system requirements to identify all external data sources and destinations

4. Context Diagrams
Record the name of the entities and the name and content of the data flows, and the direction of the data flows.
What makes one system more complex than another is the number of components, the number of levels, and the degree of interaction among its processes, entities, data stores, and data flows

5. Context Diagrams
Shows the overall business process as just one process.
The process is given the number zero.
Shows all the outside entities that receive information from or contribute information to the system

6. Context Diagrams Each context diagram must fit on one page.
The process name in the context diagram should be the name of the information system.
Use unique names within each set of symbols.
Do not cross lines.
Use a unique reference number for each process symbol.

7. Developing DFDs 1. Context Diagram for Pizza Hut food ordering system
CUSTOMER
KITCHEN
Food Order
Customer Order
Receipt
Management Reports
RESTAURANT
MANAGER

8. Creating a Set of DFDs
Create a graphical model of the information system based on your fact-finding results
Performing three main tasks
Step 1: Draw a context diagram
Step 2: Draw a diagram 0 DFD
Step 3: Draw the lower-level diagrams

9. Creating a Set of DFDs Draw a Diagram 0 DFD Diagram 0
Zooms in on the context diagram and shows major processes, data flows, and data stores
Must retain all the connections that flow into and out of process 0
Each process has a reference number
Diverging data flow

10. Draw the Lower-Level Diagrams
Creating a Set of DFDs
Draw the Lower-Level Diagrams
Must use leveling and balancing techniques
Leveling
Uses a series of increasingly detailed DFDs to describe an information system
Exploding, partitioning, or decomposing

11. Data Flow Diagrams Lower-Level Diagrams Balancing
Ensures that the input and output data flows of the parent DFD are maintained on the child DFD

12. Developing DFDs 1. Context Diagram for Pizza Hut food ordering system
CUSTOMER
KITCHEN
Food Order
Customer Order
Receipt
Management Reports
RESTAURANT
MANAGER

13. Developing DFDs 2. Level-0 Diagram for Pizza Hut food ordering system
1.0
Receive &
Transform
Customer
Food Order
CUSTOMER
KITCHEN
Customer Order
Food Order
Receipt
2.0
Update
Goods Sold
File
3.0
Update
Inventory
File
Inventory
Data
Goods Sold
Formatted
Goods Sold Data
Formatted
Inventory Data D2 D1
Goods Sold File
Inventory File
4.0
Produce
Management
Report
Daily Inventory Depletion Amounts
Daily Goods Sold Amounts
manager
Management Reports

14. Developing DFDs 2. Level-1 Diagram for Pizza Hut food ordering system
1.1
Receive
Customer
Order
1.3
Transform
Order to
Kitchen
Format
Customer
Order
Customer
Order
Food Order
Customer
Order
1.5
Generate
Inventory
Decrements
Customer Order
Inventory Data
Customer Order
1.2
Generate
Customer
Receipt
1.4
Generate
Goods Sold
Increments
Receipt
Goods Sold Data

15. Rules Governing Data Flow Diagramming

16. Rules Governing Data Flow Diagramming Process
Process cannot have outputs only. It means it is making data from nothing
Only a source should have outputs without inputs

17. Rules Governing Data Flow Diagramming Process
No Process can have only inputs
If an object has only inputs, then it must be a sink.

18. Rules Governing Data Flow Diagramming Process
A Process should have a verb phrase label
Generate
Orders

19. Rules Governing Data Flow Diagramming Process
Data cannot move directly from one data store to another data store.
Data must be moved by a process
Generate
Orders

20. Rules Governing Data Flow Diagramming Process
Data cannot move directly from an outside source to a data store
Data must be moved by a process which receives data from the source and places the data into the data store
Generate
Orders
Source
Source

21. Rules Governing Data Flow Diagramming Process
Data cannot move directly to an outside sink from a data store
Data must be moved by a process
Generate
Orders
Sink
Sink

22. Rules Governing Data Flow Diagramming Process
A data store has a noun phrase label
Inventory

23. Rules Governing Data Flow Diagramming Process
A data store A data store must have at least one incoming and one outgoing data flow.
Inventory

24. Rules Governing Data Flow Diagramming Process
Source/Sink
Rule 9:
Data cannot move directly from a source to a sink
It must be moved by a process
Generate
Orders
Source
Sink
Source
Sink

25. Rules Governing Data Flow Diagramming Process
Source/Sink
Rule 10:
A source/sink has a noun phrase
Supplier

26. Rules Governing Data Flow Diagramming Process
A data flow has only one direction of flow between symbols
It may have both direction flows between a process and a data store to show a read before an update
Later it is indicated by two separate arrows
Generate
Orders
Generate
Orders

27. Rules Governing Data Flow Diagramming Process
A fork in a data flow means that exactly the same data goes from a common location to two or more different processes, data stores, or sources/sinks.
There should not be a variation in duplication A A B A

28. Rules Governing Data Flow Diagramming Process
A joint in a data flow means that exactly the same data comes from any of two or more different processes, data stores, or sources/sink to a common location
Only similar data flows can be joined A A B A

29. Rules Governing Data Flow Diagramming Process
A data flow cannot go directly to the same process it leaves.
There must be at least one other process which handles the data flow, produces some other data flow, and returns the original data flow to the beginning process B A A A C

30. Rules Governing Data Flow Diagramming Process
A data flow to a data store means update (delete or change)
Generate
Orders
Delete or changed data

31. Rules Governing Data Flow Diagramming Process
A data flow from a data store means retrieve or use
Generate
Orders
Retrieve/Use

32. Rules Governing Data Flow Diagramming Process
A data flow must have a noun phase label
Updated stock

33. DFDs Exercises

34. Data Flow Diagrams
Examples of correct uses of data store symbols in a data flow diagram. [1]

35. Data Flow Diagrams

36. Data Flow Diagrams Entity can be connected with a process only
Examples of correct uses of external entities in a data flow diagram.[1]

37. Data Flow Diagrams

38. Data Flow Diagrams

39. DFD Errors

40. DFD Errors