In the last decade, enterprise architecture has grown into an established approach for management of organization-wide information systems. Enterprise architecture is model based, in the sense that diagrammatic descriptions of the systems and their environment constitute the core of the approach. This book emphasizes the decision-supporting potential of enterprise architecture. It presents a comprehensive set of enterprise architecture models as well as how these may be used to assess important properties of the represented systems, such as availability, modifiability, performance, and information security. The book is directed at two groups of readers. Students are provided a background to enterprise information systems and the problems associated with their management. Practitioners will find hands-on descriptions on how to get started with enterprise architecture in their company.