Definition: OLAP

(OnLine Analytical Processing) Decision support software that allows the user to quickly analyze information that has been summarized into multidimensional views and hierarchies. OLAP tools are used to perform trend analysis on sales and financial information. They enable users to drill down into masses of sales statistics in order to isolate products that are the most volatile.

OLAP and MOLAP
Traditional OLAP products are also called "multidimensional OLAP" (MOLAP) because they summarize transactions into multidimensional views ahead of time. Data are organized into a cube structure that can be rotated by the user, which is particularly suited for financial summaries. Queries are fast because the consolidation has already been done.

Relational OLAP (ROLAP)
Relational OLAP tools extract data from relational databases. Using complex SQL statements against relational tables, ROLAP is able to create multidimensional views on the fly. ROLAP tends to be used on data that has a large number of attributes, where it cannot be easily placed into a cube structure. For example, customer data with numerous descriptive fields are typically ROLAP candidates, rather than financial data.

Database OLAP and Web OLAP (DOLAP and WOLAP)
A database OLAP refers to a relational DBMS that is designed to host OLAP structures and perform OLAP calculations. Web OLAP refers to OLAP data that is accessible from a Web browser. See MDX.