Real-time systems are defined as those for which correctness depends not only on the logical properties of the produced results, but also on the temporal properties of these results. In a database, real-time means that in addition to typical logical consistency constraints, such as a constraint on a data item's value, there are constraints on when transactions execute and on the freshness' of the data transactions access.
The challenges and tradeoffs faced by the designers of real-time database systems are quite different from those faced by the designers of general-purpose database...