The figure here shows the level 1 DFD, which is the decomposition (i.e. break down) of the Supermarket App process that is shown in the Context DFD. Read through the diagram and then we will introduce some of the key concepts based on this.
The Supermarket App Data Flow Diagram example contains five processes, one external entity and three data stores. Although there is no design guideline that governs the positioning of shapes in a Data Flow Diagram, we tend to put the processes in the middle and data stores and external entities on the sides to make it easier to comprehend.
Posted by: Ricardo Poole