A constant pattern in the corporate environment is the gathering of resources, but with the free exchange of information inherent in community-based projects, the pattern of choice is the dispersal of resources. This presents certain design challenges, which manifest themselves in the Unix-style "small sharp tools" specialization approach, "bottom-up design", and most importantly in easy-to-obtain, shared, free standards for data interchange between programs. When every train car is to be made by a separate builder, it is essential that the rail gauge is constant and known.