A data flow diagram (DFD) is a graphical representation that shows how data flows through an information system by depicting external entities, processes, data stores, and data flows. DFDs consist of a set of diagrams and supporting text that visualize how input data is transformed through functional processes to produce output results. The key symbols used in a DFD are external entities, processes, data flows, and data stores.

1. • A data flow diagram (DFD) is a graphical
representation of the "flow" of data through an
information system,
• DFDs can also be used for the visualization of data
processing (structured design).
• They consist of two parts: a set of Data Flow Diagrams
(DFDs) and a set of associated textual descriptions.
• Data Flow Diagram (DFD) is an important technique
for modeling a system’s high-level detail by showing
how input data is transformed to output results
through a sequence of functional transformations.

2. e
Manager
Purchase Order
External 1 Stock Clerk
Stock List
Entities P.O. Order
Stock
Stock List M2 Stock
File
d
Supplier Processes Purchase Order Data Stores
Delivery
2 Stock Clerk
Purchase Order
Receive Orders M1
Stock Cabinet
*
Matched Orders
e
Manager Delivered Goods
3 Cashier
Sell Sold Goods M2 Stock
Stock File
*
Bought Goods
a
Customer

3. • The DFD is a diagram that consists principally of four
symbols, namely the external entity, the data flow,
entity flow
the process and the data store
• External entities (source/destination of data) are
represented by squares; Processes (input-processing-
output) are represented by rectangles with rounded
corners; Data Flows (physical or electronic data) are
represented by arrows; and finally, Data Stores
(physical or electronic files) are represented by open-
ended rectangles.

4. d
Supplier

5. Customer Details
Data Flow (usual)
Bi-directional Flow (rare)
Flow Between External Entities Goods
(for convenience)
Resource Flow (for convenience) Cosmetics

6. 3 Cashier
Sell
Stock

7. D3 Suppliers
Stock
M1 File
T1 Unpaid Invoices
D1 Orders D1 Orders

8.  A sequence diagram is a kind of interaction
diagram that shows how processes operate
with one another and in what order.
 Sequence diagrams are sometimes called event
diagrams, event scenarios, and timing
diagrams.

10.  Activity diagrams are graphical
representations of workflows of stepwise
activities and actions with support for choice,
iteration and concurrency.
 Activity diagrams can be used to describe the
business and operational step-by-step
workflows of components in a system. An
activity diagram shows the overall flow of
control.

11. Sales
Fulfillment