Context Diagrams
IPT 2010
Context Diagrams
Context diagrams are used to represent entire information systems. The system is shown as a single process along with the inputs and outputs (external entities) to the system. The external entities are connected to the single process by data flow arrows.
Context Diagrams
A context diagram is often the starting point of a data flow diagram. Context diagrams show the flow of data in a system.
3 Symbols
The Process
The Data Flow
The External Entity
Process
Single Process: A circle is used to represent
the entire system.
Data Flow
Data Flow: An arrow is used to represent
the flow of data between the
process and external entities.
External Entity
External Entity: A square or rectangle represents
any person or organisation that sends data
to or receives data from the system.
Example
Finding a book in the library
Borrower
Search
Borrower
Book Details
Call Number
Example
A context diagram for a retail sales company company.
Head
Office
Office
Sales
Dept.
Purchase
Dept.
Accounts
Warehouses
Sales
Division
Division
Suppliers
Banking
Activity
A marking system is a process used to determine the result of an assessment task. Students complete the assessment task and receive a mark from the marking system. A teacher constructs a marking scale for the assessment task and receives each student’s mark. Construct a context diagram for the marking system.
Textbook
Page 270- ‘Consider the Following”
~Read as a whole class~
HSC Style Question
Development of a new information system is being considered. They system is used to assess the impact of various types of security used to protect different types of residential and commercial buildings in various locations. The system aims to provide information to insurance companies to enable them to accurately modify the amount their customers pay for insurance based on the insured building’s security features, location and type. The results from the system will be sold to insurance companies who can then download updated information each month.
a) Draw a context diagram for the proposed system based on the above description
Suggested Solution
Building owners
and
tenants
Security
Assessment
System
Assessment
Insurance
Companies
Building Type, Location,
Security Features
Results
How did you go??
Textbook Reading
Read pg. 395-396.
Group Task Discussions pg.396
Group Task Activity pg.36