The key part of the Data Flow Diagramming method (as I was taught it, anyway) was not graphical: the Data Dictionary. This was, as the name implies, a dictiona

The key part of the Data Flow Diagramming method (as I was taught it, anyway) was not graphical: the Data Dictionary. This was, as the name implies, a dictionary that was the single source of truth for definitions of data items: meaning, representation, meaning of enumerated values, synonym and their business contexts, examples, caveats, etc. Easily implemented as a single table in your database. Never done these days, although it would probably simplify learning a system quite a lot.