Data Flow Diagram is the widely used system design tool which aids in depicting flow of logic and data (commonly called process flow) within the targeted system, in various levels of detail. Level 0 DFD is usually called ‘Context Diagram’ and it gives the highest level view. Starting from the black box in Context Diagram, we explode out into further detail as level 1 and level 2 DFDs. We combine detailed DFDs (also called primitive diagram) of various system components and create the System Diagram (are actually considered as level 1 data flows since they show flows at a much higher level). An event decomposition diagram (EDD) is usually drawn after context diagram, to identify major system functionalities as a hierarchical diagram. It is generally considered as a level 1 data flow. Below is the depiction of sample Context Diagram, EDD, DFD and system diagram. The designed system is a typical IT call management system, which is titled here as CTTS.
Even Decomposition Diagram:
Detailed DFD (Primitive Diagram for Service Request Function):
System Diagram (Collection of detailed DFDs representing a whole system):