The Store may be considered as the place of deposit in which the numbers and quantities given by the conditions of the question are originally placed, in which all intermediate results are provisionally preserved and in which at the termination all the required results are found.

Charles Babbage, 1837

The concept of using a data storage area to support the calculations of a general-pur-pose computer date back to the mid-nineteenth century. The year 1837 is not a mistake for the above quotation! The source is a paper titled On the Mathematical Powers of the Calculating Engine, published by Charles Babbage in 1837. This paper details the Analytical Engine, a plan for a mechanical computer. The organization of the Analytical Engine became the inspiration for the ENIAC more than one hundred years later. The ENIAC was the first general-purpose electronic computer, which in turn influenced the organization of computers in common use today.

Surprisingly, this quote from well over 150 years ago is descriptive of the current data warehousing and online analytical processing (OLAP) technologies. The original data is placed in the fact tables and dimension tables of a data warehouse. Intermediate results are often calculated and stored on disk as materialized views, also known as Materialized Query Tables (MQT). The materialized views can be further queried until the required results are found. We focus on two decision support technologies in this chapter: data warehousing and OLAP. We detail the physical design issues that arise relative to these decision support technologies.