  Software development processes are subject to variations in time and space,
variations that can originate from learning effects, differences in application
domains, or a number of other causes. Identifying and analyzing such
differences is crucial for a variety of process activities, like defining and
evolving process standards, or analyzing the compliance of process models to
existing standards, among others. In this paper, we show why appropriately
identifying, describing, and visualizing differences between process models in
order to support such activities is a highly challenging task. We present
scenarios that motivate the need for process model difference analysis, and
describe the conceptual and technical challenges arising from them. In
addition, we sketch an initial tool-based approach implementing difference
analysis, and contrast it with similar existing approaches. The results from
this paper constitute the requirements for our ongoing development effort,
whose objectives we also describe briefly.
