Mondrian is an open source OLAP (online analytical processing) server,written in Java.It supports the MDX (multidimensional expressions) query languageand the XML for Analysis and olap4j interface specifications.It reads from SQL and other data sourcesand aggregates data in a memory cache.Mondrian is used for: High performance, interactive analysis of large or small volumes of information Dimensional exploration of data, for example analyzing sales by product line, by region, by time period Parsing the MDX language into Structured Query Language (SQL) to retrieve answers to dimensional queries High-speed queries through the use of aggregate tables in the RDBMS Advanced calculations using the calculation expressions of the MDX language