Arcadia is a system engineering method based on the use of models, with a focus on the collaborative definition, evaluation and exploitation of its architecture. This book describes the fundamentals of the method and its contribution to engineering issues such as requirements management, product line, system supervision, and integration, verification and validation (IVV). It provides a reference for the modeling language defined by Arcadia. The author discusses the range of applications, from the assessment of different architectures and their suitability, to the collaboration between system engineering, specialties such as safety or security, subsystems engineering teams, software and hardware. This is illustrated by several examples of representative models which constitute a common thread.