JSON as a building block
Once interfaces are prototyped and it is time to build them it is useful to have a seperated layer in your application that serves the data that feeds into them. Seperation of the data serving from the web-interface 1) lets other independant or unrelated interfaces or applications to also be built against the response; 2) permits exposure of the data to script-based tools, i.e. where most analysis happens; and 3) lets a collaborating team focus on different areas of the application at the same time, for example one person can work on the data modelling, another on the UI/UX.