All OLAP components can work with flat dimensions. Flat dimensions, a single table as the data source. The dawn of the OLAP analysis. Developers' algorithms far from perfection, no analytical experience, mid of the nineties. Past century. But the time goes forward. The Star schema: a fact table, several dimension tables. De facto, it is a standard for those who does not need more. But the step forward was made, and the question was asked: Is it possible to use dimension tables with the hierarchy structure during the OLAP analysis? Except for "Yes", OLAP developers had no other answers. In that way, hierarchy dimensions appeared and with them - new long-expected opportunities for the OLAP analysts.