Context Diagram

A system context diagram defines the boundary between the system and its environment, showing the entities that interact with it. It represents an overview of the main interactions between the system and the outside world. Context diagram focuses on the core relationships that the system has with other external entities (systems, organizational groups, external data stores, etc.). It depicts the system as a central process, with no details of its interior structure, surrounded by interacting systems, parties, or processes. Context diagram is in fact a top-level (also known as "Level 0") data flow diagram.

A context diagram is a handy technique, especially in the early stages of the project, when they help discover the critical dependencies to better understand the situation and the scope. It is also a convenient part of the documentation of the released system. Such documentation overview assists in understanding the context of the system and serves as an information hub from where it is possible to navigate to more detailed parts of the documentation.