A variety of applications in the areas of control, navigation, mobile systems, telecommunications, and simulation depend on the timely and predictable delivery of data. Aircraft and spacecraft control are characterized by small main-memory databases with extremely short mean-latency requirements. Onboard navigation systems tend to combine a small portion of dynamic data with large amounts of static data, e.g., maps and landmark information. The same is true for many simulation environments, e.g., flight simulators or virtual test benches, where some parts of the system are simulated and some parts are physical components. In telecommunications the notion of real time is interpreted mostly statistically, i.e., a predetermined percentage of transactions must meet their deadline. Demanding requirements are imposed by mobile networks with extremely high transaction rates and short response times. A requirements analysis of real-time database systems can be found in Buchmann and Liebig (2001); Locke (1997); Purimetla, Sivasankaran, Ramamritham, and Stankovic (1995); and Raatikainen (1997).