It is a method to depict more detail in lower-level Data Flow Diagrams
It is the technique to expand or decompose DFDs into more details or levels to extract more information and identify all functional primitives until no further detail is required.
An information system can be comprised of multiple processes. Leveling partitions each process into sub-processes which identifies more details about the process with each level.
0-level DFD: it starts with context diagram which depicts the whole system as a single process e.g. Grading system.
1-level DFD: the context diagram is decomposed in this level. This means a single process is expanded into multiple processes which extracts more details about a process of a system.
2- level DFD: this level decomposes the the process of level 1 going into further details.
This decomposition and expansion continues until no further details are required and all functional primitives are identified.
