Our book is about organizational architecture and design. The intended audience includes managers and IT professionals, and graduate students of management and MIS. In addition, this book may serve as a reference for research topics - it has become popular as a resource for Master's and Ph.D. students. One hundred years ago Frederick Winslow Taylor engineered work with engineering disciplines and thus created the 20th century design discipline of Scientific Management. In this book we architect work with modeling concepts and thus create the 21st century design practice of Organization Modeling. The analytical disciplines we choose to employ are those associated with the software engineering field: contracts and object-orientation. Our central innovation is the concept of an organization molecule. An organization molecule is the building block of design. It is a managed collection of well known management concepts or domains, such as business process, information, culture, knowledge, structure, strategy, etc. - one molecule for each type of organizational domain or management concept. We may use a molecule to design a domain and create an architecture-in-the-small. Similarly, we may align several molecules into organizational patterns, creating an architecture-in-the-large. Such patterns are at the heart of an organization's competitive distinctiveness. Organization Modeling may be seen as an MIS as well as an organizational design discipline. The industrial era is giving way to the knowledge era. The industrial era organization is characterized by information processing and therefore emphasizes data creators, routine work and a machine culture. In contrast, the knowledge organization is characterized by learning, and therefore emphasizes knowledge creators, nonroutine work, and innovative cultures. The knowledge organization requires an architecture where the three domains of data, information and knowledge are clearly distinguished - designing knowledge work requires a careful intermingling of all three. Hence, we devote a great deal of attention to the architectural models underlying all three domains and how they are interrelated. This brings forth fresh design constructs such as a knowledge contract, and a whole new approach to the meaning of a business system. Finally, we advance a core organizational architecture for a successful 21st century organization, one that emphasizes culture, business processes, data, information, knowledge, people, and learning. The authors are members of the faculty at Stevens Institute of Technology located in Hoboken, New Jersey, USA. They teach in the executive information management programs at such firms as AT&T, Lucent Technologies, Solomon Smith Barney, PaineWebber, Prudential, and Pearson Education, among others.