Causality and the spatial-temporal ordering of events in mobile systems

Several mobile computing applications require that both the order of occurrence of events, and the location of their occurrence, be taken into account during decision making. Thus, processes need to track the location of nodes and synchronize their clocks. In this paper we present a framework, based on the capabilities of Global Positioning System, which provides processes with a global virtual clock and a positioning service. We introduce then the notion of space-time vector used by processes to track the mobility of nodes