MDAC 2.5 SDK - OLE DB Programmer's Reference
Chapter 22: OLE DB for OLAP Objects and Schema Rowsets

Same Member in Multiple Hierarchies

The MEMBERS rowset has two columns that indicate the member's position in the hierarchy: LEVEL_UNIQUE_NAME and LEVEL_NUMBER. However, it is possible for the same member to belong to more than one hierarchy. OLE DB for OLAP requires the MEMBERS rowset to contain a row for each occurrence of a member in a different hierarchy. For example, if the member "January" belongs to two different hierarchies, Quarters and Months, the MEMBERS rowset has two rows, for which MEMBER_UNIQUE_NAME is "January.Quarters" and "January.Months." Because the member name "January" has been qualified here in order to make it unique compared to the hierarchy name, the MEMBER_CAPTION for both rows will be the same.