External Agent in DFD

All information systems respond to events and conditions in the system’s environment. System’s environment includes external agents that form the boundary of the system and define where the system interfaces with its environment. It’s also referring to source or sink. External agents give an input to a system and receive an output from the system.

An external agent of an information system are already fixed and defined. When the system is getting big, the external agents may be changed. An external agent can be an outside person, organization unit, system or organization that interacts with a system and eternal organization It can be such as :

·         An office, department, division or individual from the same organization

·         An organization, agency, or individual that is outside the organization

·         Another business or information system

·         System’s end users or managers

The name of the entity appears inside the symbols. External agents should be named with descriptive, singular nouns such as VENDOR and ACCOUNTING SYSTEM. System analyst called an external agent that supplies data to the system a source, and an entity that receives data from a system a sink. An external entity can be a source or a sink or both, but each entity must be connected to a process by a data flow.