Chapter 14 Temporal databases

Time is ubiquitous in information systems. Almost every enterprise faces the problem of its data becoming out of date. However, such data is often valuable, so it should be archived and some means of accessing it should be provided. Also, some data may be inherently historical, e.g., medical, cadastral, or judicial records. Temporal databases provide a uniform and systematic way of dealing with historical data. This chapter develops point-based data models and query languages for temporal databases in the relational framework. The models provide a separation between the conceptual data (what is stored in the database) and the way the data is compactly represented in the temporal relations (how it is stored). This approach leads to a clean and elegant data model while still providing an efficient implementation path. The foundations of the approach can be traced to the constraint database technology [Kanellakis et al., 1995]: constraint representation is used as the basis for a space-efficient representation of temporal relations.