Th is book is about the future of systems engineering (SE). Specifi cally, it focuses on the theory and practice of what we call enterprise systems engineering (ESE). Aspects of SE that were traditionally insignifi cant or not at all known are becoming signifi cant for systems that must operate in complex enterprises. Both the generally accepted theory and practice are going through signifi cant changes. Although technology acts as an accelerator, change is not so much driven by technology as by what emerged from that technology: the interconnectedness and interdependence of today’s enterprises. We are observing problems and failures with the application of traditional SE methods to the development of complex systems. As we accumulate more such experience, ESE takes on all the earmarks of Kuhn’s scientifi c revolution [1]. Th e International Council on Systems Engineering (INCOSE) has noted that the increasing complexity in both problems and the systems required to deal with them was already stretching the validity of present SE processes [2].