Data Flow Diagram (DFD)
A Data Flow Diagram (DFD) tracks processes and their data paths within the business or system boundary under investigation. A DFD defines each domain boundary and illustrates the logical movement and transformation of data within the defined boundary. The diagram shows 'what' input data enters the domain, 'what' logical processes the domain applies to that data, and 'what' output data leaves the domain. Essentially, a DFD is a tool for process modelling and one of the oldest.
A Data Flow Diagram is useful for establishing the boundary of the business or system domain (the sphere of analysis activity) under investigation. It identifies any external entities along with their data interfaces that interact with the processes of interest. A DFD can be a useful tool (particularly when used as a top DFD - refer to Context diagram) for helping secure stakeholder agreement (sign-off) on the project scope. It is also a useful tool for breaking down a process into its sub-processes for closer analysis.
A Data Flow Diagram can be modelled early in the requirements elicitation process of the Analysis phase within the System Development Life Cycle (SDLC) to define the project scope. A DFD can also be created throughout the SDLC to investigate an aspect of the system. If necessary, each process under study within a DFD can be broken down into its sub-processes on a new DFD to show more details. A sub-process in turn can be broken down further to reveal its sub-processes on a new DFD, and so on until sufficient analysis is reached. The activity of drilling down the DFD levels is called 'functional decomposition' with the resulting new DFD referred to as a 'levelled DFD'. For example, the top level DFD (also known as a Context diagram) is a level 0 DFD, level 1 DFD refers to the initial decomposition, level 2 DFD to a second level decomposition, and so on.
Menurut artikel yg saya kutip diatas menjelaskan tentang pengertian DFD (Data Flow Diagram) beserta fungsi dan cara penggunaannya di artikel itu menjelaskan bahwa DFD pada System Development Life Cycle (SDLC) terdiri dari beberapa level di mulai dari hitungan 0 sampai selesai.