A context diagram is a data flow diagram that only shows the top level, otherwise known as Level 0. It should be noted here that at this level, there is only one visible process node that represents the functions of a complete system in regard to how everything interacts with external entities. As the context DFD template suggests, the core reason behind creating such a diagram is to get an a-glance view that shows the system as a single high-view process, with its relationship to external entities. As the DFD template suggests, the context diagram helps you identify the interfaces you need to account for, helps to identify scope, identify potential stakeholders and builds a better understanding of the context in which you are working.
