in an "inverted file" or "inverted index", the contents of the data are used as keys in a lookup table, and the values in the table are pointers to the location of each instance of a given content item. this is also the logical structure of contemporary database indexes, which might only use the contents from a particular columns in the lookup table. the "inverted file data model" can put indexes in a set of files next to existing flat database files, in order to efficiently directly access needed records in these files.