Past analyses of social systems have too often relied upon obsolete dualities such as open system/closed system. The purpose of this paper is to provide a more comprehensive analysis of the full range of boundary-maintenance operations that are at work in the modern complex social system. I first analyze the role of the boundary in Living Systems Theory, and then turn to the analysis and comparison of boundary maintenance in Social Entropy Theory. Among the topics discussed are boundary control for matter-energy flows, boundary control for information flows, types of information inflows across social-system boundaries, types of information outflows across social-systems boundaries, and types of matter-energy inflows and matter-energy outf...