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The context diagram must fit in one page.

For example, level n & n+1 must have the same inputs and outputs Guideline for Developing Data-Flow Diagram Context Diagram - Level 0 When performing top-down decomposition to a DFD to lower level DFDs, the inputs and outputs must be conserved between levels of DFDs. As shown in the Figure, DFD Leveling is first displaying the targeted system as a single process, and then showing more detail until all processes are functional primitives. Leveling is done by drawing a series of increasingly detailed diagrams until the desired degree of detail is reached. Top-down decomposition, also called leveling, is a technique used to show more detail in lower-level DFDs.

An external entity must be connected to a process through a data-flow.External entities also are called terminators because they are data origins or final destinations.The name consists of a verb, followed by a singular noun. Processes can be as simple as collecting input data and saving in the database, or it can be complex as producing a report containing monthly sales of all retail stores in the northwest region.Įvery process has a name that identifies the function it performs. There are four basic symbols that are used to represent a data-flow diagram.Ī process receives input data and produces output with a different content or form. Establishment of manual and automated systems requirements.Determination of physical system construction requirements.

DFD has often been used due to the following reasons: Structure of DFD allows starting from a broad overview and expand it to a hierarchy of detailed diagrams. The visual representation makes it a good communication tool between User and System designer. DFD graphically representing the functions, or processes, which capture, manipulate, store, and distribute data between a system and its environment and between components of a system.