The book describes a fundamentally new approach to software dependability, considering a software system as an ever-changing system due to changes in service objectives, users' requirements, standards and regulations, and to advances in technology. Such a system is viewed as an Open System since its functions, structures, and boundaries are constantly changing. Thus, the approach to dependability is called Open Systems Dependability. The DEOS technology realizes Open Systems Dependability. It puts more emphasis on stakeholders' agreement and accountability achievement for business/service continuity than in elemental technologies.