ABSTRACT
This chapter describes the concepts that have evolved significantly since the first edition and continue to evolve as new and emerging factors continue to impact infrastructure. Given a basic understanding of some of the pressures within the system and some of the upcoming challenges associated with understanding how the infrastructure is protected, one can begin to look at fragility. The chapter presents examples that show how the impacts in terms of the performance of infrastructure need to be examined in a more coordinated fashion between local (including business), regional, and national (including strategic) perspectives. The concept of interdependencies and cascading impacts has also worked in parallel and even contributed to a growing amount of research into the fragmentation and dissolution of networks. The concept of performance basically describes whether the system works with sufficient capacity to meet its demand.
