The way in which software evolves over time has been much studied and is now fairly well-understood. What has been less thoroughly studied are the processes by which information systems – containing software as one component, but also with significant human and organisational aspects – evolve. In many organisations, few information systems are built at all from scratch, but rather are modified from or built on top of existing ones or bolted together from third-party components. In practice, the old division between design, implementation and maintenance has largely disappeared. In this paper, I discuss the nature of IS evolution. I make a distinction between planned (intentional and strategic) evolution, for which we can formulate a clear process; and unplanned (emergent and externally-driven) evolution, where we can simply study the dynamics of the process and be ready for events
