The article deals with an in practice frequently applied procedure: Th
e modelling and redundant storage of aggregated data, obtained from re
ady excisting basic data. Existing modelling techniques are applied to
aggregated data; they have to be extended to capture more meaning. Pa
rameters and problems are predented, influencing the decision on the p
roduction and redundant storage of aggregated data. Further different
types of storage of aggregated data are shown.