A context diagram helps stakeholders understand where the software system fits in the world. Context diagrams show the people and systems that interact with the software system you are responsible for developing.

Benefits

• Provide a high-level overview of the systems and stakeholder groups the system directly interacts with or relies on.

• Make the boundary between the system you’re building and the outside world obvious to stakeholders.

• Use as a natural entry point for learning about the system’s architecture.

• Ensure everyone is aware of and agrees with the general system scope.

Description

In a typical context diagram, the system you are developing goes in the center. Draw the various people, software systems, and hardware your system will use or interact with around the system whose context you are describing. Arrows are used to show the relationship among these various elements to describe the overall circumstances in which the system you’re designing lives.

Context diagrams can take on many forms and need not be only a box-and-line diagram. Any graphical depiction that can show where the system fits in the world can work, including drawings, storyboards, cartoon strips, and photographs. Some teams have even experimented with using video and animation to describe a system’s context.

Guidelines and Hints

• It’s OK to use informal notations. The most important thing is to communicate effectively.

• Show people and systems relevant to the system you are designing.

• Label arrows to tell how two things are related.

• Include a legend to describe the notations in the diagram.

Example

Here is a possible context diagram for Project Lionheart: