Business Intelligence: OLAP Tool Selection
OLAP tools are geared towards slicing and dicing of the data. As such, they require a strong metadata layer, as well as front-end flexibility. Those are typically difficult features for any home-built systems to achieve. Therefore, my recommendation is that if OLAP analysis is part of your charter for building a data warehouse, it is best to purchase an existing OLAP tool rather than creating one from scratch.
Before we speak about OLAP tool selection criterion, we must first distinguish between the two types of OLAP tools, MOLAP (Multidimensional OLAP) and ROLAP (Relational OLAP).
1. MOLAP: In this type of OLAP, a cube is aggregated from the relational data source (data warehouse). When user generates a report request, the MOLAP tool can generate the results quickly because all data is already pre-aggregated within the cube.
2. ROLAP: In this type of OLAP, instead of pre-aggregating everything into a cube, the ROLAP engine essentially acts as a smart SQL generator. The ROLAP tool typically comes with a 'Designer' piece, where the data warehouse administrator can specify the relationship between the relational tables, as well as how dimensions, attributes, and hierarchies map to the underlying database tables.
Right now, there is a convergence between the traditional ROLAP and MOLAP vendors. ROLAP vendor recognize that users want their reports fast, so they are implementing MOLAP functionalities in their tools; MOLAP vendors recognize that many times it is necessary to drill down to the most detail level information, levels where the traditional cubes do not get to for performance and size reasons.
So what are the criteria for evaluating OLAP vendors? Here they are: