Back in the old days (4 years ago)
It was a trend with the traditional model of app development that the app dev team would take a particular dominance over the presentation layer, as it was rightly so, their domain. The deign teams of the time resorted to non-code ways of communicating their intentions as to influence the design. The 'comp' and 'red-line' documents were the primary resource of communication. Practices that are not all that dead, people still do this stuff you know.
We all know by now that these processes don't really work. They are fraught with error and caused countless hours of frustration between designers and developers. Witness the rise of the 'designer - developer' or 'The Designer w