Context Diagram

The Context Diagram shows the system under consideration as a single high-level process and then shows the relationship that the system has with other external entities (systems, organizational groups, external data stores, etc.).  


Definition courtesy of:  http://www.modernanalyst.com/Careers/InterviewQuestions/tabid/128/ID/1433/What-is-a-Context-Diagram-and-what-are-the-benefits-of-creating-one.aspx

Image courtesy of: https://www.google.com.ph/search?q=gane+and+sarson+context+diagram+symbols&hl=fil&tbm=isch&source=iu&ictx=1&fir=BHUL5J2DjjMdIM%253A%252CMrak7baNEDcx4M%252C_&usg=AFrqEzcPG0HKk69STAVO8TJVCO_6QIzNZw&sa=X&ved=2ahUKEwjO_rjB6uHcAhUDv7wKHewyALQQ9QEwAXoECAcQBA#imgrc=BHUL5J2DjjMdIM:


Common Observed Requirements:
1. An ENTITY is not allowed to connect to another ENTITY or DATA STORE.
2. A DATA STORE is not allowed to connect to another DATA STORE or ENTITY.