Information technology has had a profound infl uence on business and society. Decades of software implementation have created complex IT landscapes which are less fl exible than current business needs require.New technologies and the increased use of technology in social traffic both add possibilities and create challenges to the evolvement and governance of IT.The fi eld of architecture provides a way to manage complexity and risk and presents views of the problem and solution that can be understood by various parties. This book describes an architectural approach and a reference architecture to address these possibilities and challenges. The content is based on real experiences of professionals in the fi eld of (enterprise) information technology.The main objective of this book is to learn how to deal with the impact of new fl exible business models and technologies on both enterprise and individual project level. This should result in a comprehensive distributed IT landscape that can be managed in a controllable way.The COmmon Reference Architecture (CORA), as proposed in this book, enables fast identifi cation of the impact of new or changed business requirements on the IT landscape.