various navigational functions, involving active safety, driver assistance and location-based services require data that is not considered to be part of a map database and is likely supplied by a vendor other than that of the map provider. such data needs to be cross-referenced with the entities and attributes of the main database. however, since the auxiliary data is not necessarily compiled with the main database some other means is needed to establish cross-referencing, which is referred to as "attaching" the auxiliary data. two common approaches are function-specific referencing tables and generic referencing.