I am trying to develop a DFD level 0 and 1. But as I learned from different sources(eg. textbook, website) that some say data store and sources/sinks are not allowed in the level-1 and the rest of decomposed diagrams, but some say it can be.
Are there any criteria for DFD decomposing development?
Thanks
It's not that easy to find something useful about it online, I agree. Accordingly to Timothy Arndt and Angela Guercio in Decomposition of data flow diagrams,
Data flow diagrams are an important design aid in system development.
and
Decomposition is the top-down development of a data flow diagram starting with the system inputs and the system outputs
Personally I liked the content from Visual Paradigm on the matter to know more about DFD. About decomposition, they write
Top-down decomposition, also called leveling, is a technique used to show more detail in lower-level DFDs. Leveling is done by drawing a series of increasingly detailed diagrams until the desired degree of detail is reached.
In other words, when doing leveling the goal is
first displaying the targeted system as a single process, and then showing more detail until all processes are functional primitives.
When you ask in your question
some say data store and sources/sinks are not allowed in the level-1 and the rest of decomposed diagrams, but some say it can be
what i extract from that article in Visual Paradigm is that in a context diagram you don't want any data source but in a Level 1 it's fine (there's even one example of it there - see next image).
In fact, there's some considerations / criteria to have for DFD leveling: unique names for levels, no cross line, numbering convention, ...
I suggest you to have a look as well at this article from Visual Paradigm which explains DFD by using a food ordering system as an example.
