Some Lessons in Specifying Interfaces

Having suitable software interfaces between the various layers of a project - -- whether the user-level GUI or a low-level driver - can be a point of weakness in a project. The development path tends to be from the lowest hardware level upwards. Our recently completed telescope control system project on the AAT turned this aspect completely around, with interfaces specified as much as possible by their users rather than their implementors. It started with the end users specifying the final product in great detail, even having them create the initial prototype GUI, and worked down through the layers, ending with the applications programmer specifying the driver interfaces for the hardware. This proved to be a very successful approach.