A process modeling tool that depicts the flow of data through a system the work or processing performed by the system When to use DFDs? Help you to understand the system Make a complex process clear Communicate your understanding Find the data used in the system Show the flow of data within a system and its transformation DFDs store: where data begins how data gets transformed through processes where data finishes DFDs do not store: how the process occurs who does it Data Flow Diagrams are only concerned with DATA