Debug your Requirements

I'm an old school data flow diagrammer from the CASE methodology days, but I learned a few tricks with DFD's that make them a tool I can't be without on large projects. I use them to debug my flow of data. You can do this during any of the phases that add more information to the process. If you use bubbles (circles) to indicate a process, anything going into the process is an input and anything going out is an output. Pull on the outputs by asking yourself "Can I produce this output with the inputs that are feeding this process?" Sometimes I'll ask the business users "If I put you in a room with just __(the inputs mentioned in the process)__ would you be able to produce ___(the output)__?"

Data Flow Diagrams

I ran into a web site that shows a good data flow diagram that seems fairly simple to follow. I prefer using simpler flow lines (e.g., visio DFD makes this easy)

http://www.umsl.edu/~sauter/analysis/dfd/dfd.htm

It also goes into the gory detail behind the diagram.