Cloud computing has proven to be extremely useful in practice.Both the cloud-service-provider industry and its business, scientific, and consumer applications have grown exponentially. However, there are also benefits to be gained from viewing cloud computing abstractly: understanding its fundamental behaviors, but also its limitations. After a five-year run, this is the last issue of IEEE Cloud Computing. However, it is to be hoped that this final article contains the seeds of some ideas that others will find interesting and productive, so as to continue research to formalize such a theory. In effect, this article lays the foundation for future research by encapsulating much of this columns last five years into a comprehensive, integrated theoretical framework.