What is temporal data?
In a table with temporal support, the header represents a predicate with at least one time parameter that represents when the rest of the predicate is valid—the complete predicate is therefore a timestamped predicate. Rows represent timestamped propositions, and the valid time period of a row is expressed with one of two attributes: since (for semi temporal data), or during (for fully temporal data); the latter attribute is usually represented with two values, from and to.
The following shows the original and two additional timestamped versions of an exemplary Suppliers table.
Figure 7.1: Original Suppliers table and two tables with temporal support
From the original table header, you can read a predicate saying that a supplier with identification supplierid, named companyname, having contact contactname, and so on, is currently our supplier, or is currently under contract. You can pretend that this supplier is the supplier forever, from the beginning of time until...
