Cloud computing represents an evolution in technology and a revolution in business, for when a fixed asset like a computer becomes variable and on demand, all sorts of agility and new cost structures open up. The Cloud rEvolution report tackles this new world of information technology in a four-volume series. "Laying the Foundation" (1) introduces the Cloud rEvolution and explores the core technologies that lay the groundwork for cloud computing. "The Art of Abstraction" (2) shows how abstraction loosens the IT stack for flexibility and efficiency, eying the ultimate abstraction: the cloud. "The Cloud Effect" (3) describes the impact the cloud is having on IT and business tactically and strategically. "A Workbook for Cloud Computing in the Enterprise" (4, downloadable separately) offers guidance for transitioning to the cloud, which is rapidly becoming a question of when and how, not if.