change datum 506 no longer appears in virtual hierarchy 512 having been accounted for by modifying the query as an example of step 606 suppose the received query involves aggregating performance data for nodes below the node 304 in the exemplary virtual hierarchy 308 of fig3 a this includes performance data at node 306 which was initially moved from another location and there is a change datum not shown describing this move in step 606 of fig6 this query is u201c appropriately u201d modified to a query with respect to the base hierarchy 300 fig3 a in which performance data below node 304 is aggregated along with performance data at node 306 in decision 608 it is determined whether more change data exist if so those change data are iteratively identified and used to further modify the query as in step 606 this is shown schematically in fig5 where the modified query 510 is further modified into query 514 by incorporating the remaining change datum 508 at the conclusion of the process 600 the final modified query is a query with respect to a traditional i e non virtual hierarchy that can be processed according to traditional database techniques for example in fig5 the change data 506 508 have been sequentially incorporated into a modified query 514 that ultimately can be processed with respect to the base hierarchy 504 the methods or processes described above and steps thereof may be realized in hardware software or any combination of these suitable for a particular application the hardware may include a general purpose computer and or dedicated computing device the processes may be realized in one or more microprocessors microcontrollers embedded.