Temporal Database in Depth:
Time and the Data Warehouse

by Chris Date


Two recent trends, the plummeting cost of storage and the widespread adoption of Data Warehouse technology, have led to an increasing interest in Temporal Databases; indeed, the idea of maintaining and processing historical data has become not just a goal but a reality for many organizations.
As a consequence, the ability to deal properly with the time dimension in databases as become an increasingly important practical problem. Yet today's DBMS products offer absolutely nothing to help with this important requirement. What's more, the database research community has largely failed in this regard as well; many approaches have been proposed, but they have all have proved deficient in one way or another. Help is on its way, however.
This seminar describes a new approach to the problem thet looks set to address the (surprisingly complicated!) issue of proper temporal support, an approach that, let it be said immediately, fits squarely into the classical relational tradition.

Note: Since no commercial products support that new approach as yet, this seminar might be regarded as somewhat theoretical. But the Relational Model too was once "just theory"!
Learning about the new temporal approach now is like learning about the Relational Model before there were any relational products. And just as relational knowledge was helpful (with database design, for example) even before there were any relational products, so temporal knowledge can be helpful with similar matters now, even in the current absence of temporal products.

Main Topics

  • Time and the database
  • Intervals and interval attributes
  • Packing and unpacking relations
  • Effect on relational algebra
  • Temporal database design
  • Temporal constraints
  • Temporal queries
  • Temporal updates
  • Stated times and logged times