The present invention relates to a method for ensuring data consistency upon mapping of a hierarchical data format to a relational database management system.According to the invention, a method for ensuring data consistency upon storage of a data item in a database, the data item having an identifier and a locator for linking the data item to a destination, whereby the identifier and the locator are stored in the database in addition to the data item, comprises the steps of: checking (11) whether the current combination of identifier and locator has already been stored in the database, and using (12) the stored combination of the data item if this is the case, in case the current combination of identifier and locator has not yet been stored in the database, checking (13, 15) whether either the identifier or the locator has already been stored in the database, replacing (14, 16) the current combination of identifier and locator with a univocal combination if this is the case, and storing (17) the univocal combination together with the data item, and storing (17) the current combination of identifier and locator together with the data item else.