The Mysteries of Goal Decomposition

Goal decomposition structures lie at the heart of goal modeling languages such as i*. High-level goals of stakeholders are recursively decomposed into lower level ones and eventually into leaf level tasks to be performed by agents. The decomposition structure can also develop through a bottom up approach whereby higher-level goals are introduced as justifications for existing low-level ones. The very concept of decomposition, however, both as process and as artefact is rarely questioned in requirements engineering. In this paper, we argue that it may be of value to give a closer look into goal decomposition and clarify what we actually know about it and what is yet to be understood. We report on an on-going effort to identify empirical work on decomposition coming from various research fields, hoping to find such evidence. We then pose some research questions that we believe need to be pursued in order to improve our understanding of goal decomposition.