Requirements change has always been an important, aspect of Requirements Engineering. However, the field of Requirements Evolution has not been established. To understand Requirements Evolution, its manifestation, and its research implications, we conducted an exploratory case study based on a large-scale software program1. The case study allowed us to identify important aspects of Requirements Evolution that have not been addressed, such as the life cycle and the continuity of requirements. Based on our observation, we propose a framework for understanding and conducting research in Requirements Evolution.1Due to confidentiality concerns, the software product and its vendor will remain anonymous in this thesis. They will be addressed as The Software Product (TSP) and The Company (TC). All information regarding TSP is scaled to maintain anonymity.