Author: Alexey Makhotkin squadette@gmail.com. (Word count: 3200). A common problem in business-oriented database design: keeping the history of values of a certain data attribute. For example, we may want to track the price of various goods, as they change with time. Many other tasks could be reduced to this problem: for example, when people change their address in the government database, we may want to keep track of previous addresses.
