Business information system architecture is a field positioned between the fields of enterprise architecture and software architecture. Enterprise architecture typically takes the more business-oriented point of view, where designing the structure of information systems is a final or implicit step. Software architecture departs from software engineering and focuses on the technical design of detailed software structures. Business information system architecture covers the middle field, connecting the two, and focuses on structuring business-oriented application landscapes. This middle field is where many organizations are currently struggling with making the right choices - a challenge that is made harder by the growing complexity of system landscapes and by quickly evolving possibilities of digital technology. This book addresses this important and challenging domain by providing the conceptual tools and reference structures to deal with this complexity and to abstract from individual technologies. The concept of architecture is explained from different points of view. The various dimensions are discussed that one needs to understand to effectively analyze and design architectures. Structures for architecture are explained in the categories of architecture styles, architecture patterns and reference architectures. Architecture frameworks, specification techniques, methods and principles are placed and treated in their mutual relationships. The important distinction between applications and infrastructure is highlighted. Architecture designs of several classes of concrete systems are covered. Technologies for architecture embodiment are discussed with a special emphasis on middleware technologies. The topics are illustrated with detailed examples.