I've recently come across an article I wrote back in October 2003 for SAP Design Guild. The text deals with the xApps design approach we were following then; driving product definition and design through rapid prototyping. In the article I describe the process we were using – quite successfully, I'm proud to say. From the introduction:
In the following text, I describe the prototype-based design methodology used by SAP's xApps Design Group. I explain the prototype development life cycle, discuss the advantages and disadvantages of different prototypes and prototyping materials, and illustrate how the prototype approach fits into SAP's xApps software development life cycle.