This book focuses on software architecture and the value of architecture in the development of long-lived, mission-critical, trustworthy software-systems. The author introduces and demonstrates the powerful strategy of “Managed Evolution,� along with the engineering best practice known as “Principle-based Architecting.� The book examines in detail architecture principles for e.g., Business Value, Changeability, Resilience, and Dependability.  The author argues that the software development community has a strong responsibility to produce and operate useful, dependable, and trustworthy software. Software should at the same time provide business value and guarantee many quality-of-service properties, including security, safety, performance, and integrity. As Dr. Furrer states, “Producing dependable software is a balancing act between investing in the implementation of business functionality and investing in the quality-of-service properties of the software-systems.�  The book presents extensive coverage of such concepts as:  Principle-Based Architecting  Managed Evolution Strategy The Future  Principles for Business Value  Legacy Software Modernization/Migration  Architecture Principles for Changeability  Architecture Principles for Resilience  Architecture Principles for Dependability  The text is supplemented with numerous figures, tables, examples and illustrative quotations. Future-Proof Software-Systems provides a set of good engineering practices, devised for integration into most software development processes dedicated to the creation of software-systems that incorporate Managed Evolution.