What is Mondrian?
It is a ROLAP server (Relational Online Analytical Processing). It is based on Java and is in the domain of reporting and data warehousing. It is useful when we use for analysis that involves drilling down data. It’s an open source OLAP (Online Analytical Processing) server and supports MDX (Multi-Dimensional Expression) query language. The Mondrian schema is universal metadata descriptor supported by almost any OLAP client tool.
Connecting to Mondrian Engine
Mondrian is an OLAP server which maintains data in a multidimensional fashion. In order to access any of the existing cube, we need some client (reporting tool). It is in between report and actual data warehouse. It contains the Business Layers or Metadata of data warehouse. We can put the query using some reporting tool (Pentaho Report Designer) and fetch the data from data warehouse to publish it on the report using Multi-Dimenisonal Expression.
As Mondrian supports MDX (Multi-Dimensional Expression) query language, any MDX supported OLAP client can be used. Also, there are dedicated connectors to certain BI applications like Jaspersoft by using which we can establish the connection. Mondrian is an open source OLAP engine and one can connect to it from the code using its rich API. But the easiest way would be to use their own client viz Pentaho Schema Workbench (PSW) by using which we can access the data residing at analysis services.
The above layout gives a brief insight on designing the cube and how to put the query. We can also see the http UI which is through the client. Using MDX we make a connection, which is then parsed and validated for sending results to client layer. The Schema XML is formed when we design a cube. Similarly, we have the Star Layer and Dimensional Layer. Once we get the connection, MDX validates and parses it to the SQL database through JDBC connection which will enable us to get the data back to the client. Pentaho Schema WorkBench is a design tool for Mondrian client by Pentaho, which gives GUI for designing OLAP cube and generates XML format. It can be done manually if the user understands the XML structure.
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