Download - Context Diagrams
Context DiagramsIPT 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 SymbolsThe Process
The Data Flow
The External Entity
Process
Single Process: A circle is used to representthe 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 representsany person or organisation that sends data
to or receives data from the system.
ExampleFinding a book in the library
BorrowerSearc
hBorrower
Book Details Call Number
ExampleA context diagram for a retail sales company
company.HeadOffice
Office
SalesDept
.
Purchase
Dept.
Accounts
Warehouses
SalesDivisio
n
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 QuestionDevelopment 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
SecurityAssessme
ntSystem
Assessment
InsuranceCompanies
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