According to my teacher,

A CONTEXT diagram NEVER shows what goes on INSIDE a system! It only shows the EXTERNAL entities and the circle is the SYSTEM BOUNDARY. ie the boundary between what is INTERNAL to the system and what is EXTERNAL to the system.

In the context flow diagram I'm given, driver entity is not shown. Yet the transcript says

At the end of the day, the manager uses the bookings database to allocate a bus and a driver to each tour. The passenger lists are then emailed to the drivers and a copy is placed in the Daily Tours file.

Note that the manager is part of the system. Emailing of the list is a data so there should be a data flow (that's what I think).

My question is, is there such thing as an "internal entity" that does not appear in Context Flow Diagram, but appears in the Data Flow Diagram Lvl 0?

Please migrate the post if this question if off-topic in this stackexchange

  • 1
    The terms Context Diagram and DFD Level 0 are synonymous: different names for the same thing, so there cannot be something on one that isn't on the other. Were you perhaps asking about CFD vs. DFD Level 1 or greater? – Erik Eidt Sep 20 '18 at 17:48


Internal entity

An entity within the system that transforms data. Includes, for example, accounting clerks (persons), departments (places), and computers (things)

Source: Gelinas, Ulric J., et al. Business Processes and Information Technology. Orange Grove Texts Plus, 2008.

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