Embodiments relate to systems and methods for aggregating data from data sources according to a hierarchical mapping generated from dimensions of the data sources. A set of applications such as online analytical processing (OLAP) applications can access the combined data of a set of multi-dimensional data sources via a transform engine. The set of data sources can be configured with diverse dimensions and associated data, which in general do not reflect a strictly hierarchical structure. In embodiments, the transform engine can combine or aggregate the set of data sources using common dimensions or data points, and build an index into a transform table reflecting the hierarchical level of dimension from each data source in a combined hierarchical mapping. An OLAP or other application can therefore perform searches, sorts, and/or other operations on the combined hierarchical mapping based on the resulting ordering of data, even when the original multi-dimensional data sources do not contain an explicit common hierarchy.