Data Flow Diagram (DFD):
It is a logical model that
describes what take place in an existing system, or proposed system; it does
not specify how the activities are accomplished.
It
shows the flow of data and the flow of logic involved.
Characteristics of DFD:
i.
It focuses on the process that transforms incoming
data flows (Input) into outgoing data flows (Output).
ii.
It shows the passage of data through the system.
iii.
This diagram also known as bubble chart.
iv.
DFD supports a top down approach for analysis that is
an analyst begins with general understanding of system then draws each
component’s details.
Symbols used in DFD:
1. External
Entity:
It
is a source or destination of data; it may be person, organisation or other
entity that interact with the system.
For
ex: Customer, supplier;
The entity supplying data is known
as source & those that consume data or give output are called sinks.
2. Data
Flow/Flow line:
It
shows how data travels from one point to another point in diagram.
3. Process:
It
shows the transformation of input data flows to output data flows.
All processes are numbered in DFD
for easy identification. Numbering follows a left to right convention. Name of
the process describes what happened to the data as it flows through the
process.
4. Data store:
It is
warehouse for data
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