Context and Data Flow Diagram Symbols

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Context Diagrams
Context Diagrams are used in the Analysis and Design
phases as an analysis and design tool used to analyse
processes occurring in a current information system and
also to design a new information system.
They help in identifying where problems may be
occurring in an information system.
There are three symbols used in these diagrams:
Data Flow
Booking

Data flows describe the data being
transferred, not the processing of the data.
 E.g. “booking” is used rather than “validate
booking”.
 “Validate booking” is a process whereas the
“booking” itself is the data.
The whole system and a process
The whole system
Booking system

The oval shape is used to represent the
whole information processing system
(Context Diagram)
External Entity
students

People, programs, organisations, other info
systems that provide data to the system or
receive output from the system.
 Nouns are used to name external entities.
 External entities are things that are external
to the system in question.
Context Diagrams
Bookings
Invoice
Restaurant
System
Diners
Orders
Suppliers
Payment

The highest level of the data flow diagram.

General description of the system and its relationship
with “the outside world.”