In order to produce output tables as shown on the previous slide, the relational database has to be queried by the researcher. The data have to be transformed from the relational structure to the aggregate structure of the output table.

Since the relational model is optimized to store detailed information on individuals efficiently and without contradictions, it requires a good understanding of the abstract data model for data-extraction.

This task has proven to be quite challenging and too time consuming for the normal demographic researcher. Normally the technical staff is being asked to design the queries, which is causing an enormous delay before the results come in.