Data Flow Diagram Level 0 and 1: Draw Both, Step by Step (Full Example)

A data flow diagram shows where data comes from, what changes it, where it is kept and where it goes. In this video I draw a data flow diagram level 0 and level 1 for a made-up online shop: the 4 symbols, the 5 rules, a 5-step method, and how following one piece of data found the shop's bug. Then I build the start of it in draw.io. 0:00 "We sell stuff we don't have": the problem 0:13 A DFD shows data, not steps 0:46 Explain like I'm 5: the water pipes 1:16 Four elements and the levels (BABOK) 1:55 Before you draw: three lists 2:29 The vague problem 2:56 Symbols 1-2: entity and process 3:31 Symbols 3-4: store and flow 4:05 Five rules that keep it honest 4:42 Step 1: draw level 0 first 5:14 Step 2: processes and border flows 5:46 Step 3: stores and inside flows 6:17 Step 4: check the rules, follow the data 6:44 Step 5: ask why, then fix the flow 7:21 Worked example: the finished level 1 7:58 Build it in draw.io 8:47 Confirm it and write the fix 9:19 5 common mistakes 9:48 Recap Want to build both levels in a real tool? My step-by-step draw.io context diagram and level 1 DFD tutorials are in the playlists on the channel. Note: the Online Shop, its people, numbers and prices are a made-up example (the same company as in my tool tutorials). The voice and the presenter are AI-generated (my cloned voice and avatar). Sources: BABOK® Guide v3 (IIBA, 2015), 10.13 Data Flow Diagrams: the elements (external entities, data stores, processes, data flows) and the levels (context diagram or level 0, level 1, level 2). Process bubbles follow the Yourdon / DeMarco structured analysis notation (Gane and Sarson uses rounded boxes); the data store is drawn the Gane and Sarson way, an open-ended box with an ID like D1 (in Yourdon / DeMarco it is two parallel lines). The rules (every flow touches a process, noun labels, balancing, black holes and miracles), the 5-step method and the tips are common DFD practice and the presenter's advice. #BusinessAnalysis #DataFlowDiagram #BusinessAnalyst