This context-level data flow diagram is a top-level, also known as Level 0. It only has one process node, Process 0, that generalizes the entire system's function concerning external entities. Layers of DFD Data flow diagrams can be drawn in multiple nested layers. The Content level data flow diagram will primarily show three levels: 0-level DFD, 1-level DFD, and 2-level DFD. DFD at 0 levels: It is also referred to as a context diagram. It is intended to be an abstraction view, with the system depicted as a single process with relationships to external entities.