A method that works well for this kind of analysis in my experience is to start by looking at the data, together with a business person and then ask the needed

A method that works well for this kind of analysis in my experience is to start by looking at the data, together with a business person and then ask the needed question until you can model it. "Oh so I see we have customers that are sites of large corporations, so that is a requirement" "Oh and these rows look like subsidiaries" etc