I'm designing my first Android App, and I find it very hard to actually understand what my system should actually do. I have a general Idea but when I try to tell it to others I fail to communicate what is it that the system will do.
I've written specs and created three different scenarios for different potential users and it helped me understand the main purpose of this app. I've also found that creating mock-ups gave me a better perspective of the system's objective. I've also noticed that while creating these mock-ups I focus mainly on how the app should look rather than what it should do.
I would like to now if it is a good idea to rely on GUI (Graphical User Interface) mock-ups as a way to start building a system from scratch. Will doing so help me identify classes/objects/interfaces? Will it help (when unclear) to better define the scope of the system? Is mock up building a good tool to rely on when trying to understand a new project's scope? Are there any other, better tools or steps to take when the overall goal is unclear?