In a previous post, I showed that costs data may be allocated to other departments or levels of granularity to enable cost analysis.
The allocated cost data are artificial data: the data are only a part of costs for which the data are collected at other levels of the organisation, These data are then intermediate data that are halfway between original data that are collected in the business process and the final output data that are used in the final profit and loss analysis.
In my opinion, such intermediate data should not be included in the data warehouse as they are artificially created data. If we would store such data in the data warehouse, such data could be misinterpreted as real input data. Someone from another department may use these data as being equivalent to real input data thus leading to unnecessary confusion. Anyone who does so, cannot be blamed. The data warehouse is a central data store that may be used by everyone for reporting purposes. Once included in the data warehouse, one may assume that the data represent a well analysed view upon real business events.
Therefore, to maintain a good data quality, the data warehouse is not a good environment to store such intermediate allocated data.
It is also true that the business rules to create the allocated costs can be quite complex. The owner of these business rules is the accounting department (and not the IT department). If the IT department is lured into trap to calculate such intermediate data, it is exposed at an immensely complicated situation as it must rely on specifications from the accounting department while at the same time it may be held responsible for the quality of such data. We then have a reason not to agree to calculate such allocations within the data warehouse: it is simply too complicated and the IT department does not have the knowledge to do so.
An IT department is good at three things: retrieving data, storing data and propagating data. It is not good at programming complicated business rules that may be not fully known by the owners. Hence, the IT department should not attempt to do so.