The various levels and subdivisions of geography and their interrelations may be organized for computer storage, retrieval, and update through the use of multilist structures. In this process several files are created to correspond to the different partitions of the whole space or universe. A directory is used to keep track of entities for each entity type--state, county, congressional district, etc. The “state” directory maintains 57 entries, for example, one entry for each state (50) or territory (7).

A fundamental file of unnamed, elementary entities is the basis for storing information on the geography of the space. The records of the fundamental file correspond to elementary geographic areas which are minimal intersections of entities, and which are traditionally called GTUB’s for “Geographic Tabulation Unit Base.” Each GTUB record contains pointers for several lists. Each list type corresponds to an entity type, or “county”. The county list type occupies a unique field in each record, and the value in that field is a pointer to the next GTUB with the same county code. Each list type corresponds to a partition of space and provides a method to store many specific lists of this type. The list elements are the subsequent records of the same entity.

The GTUB’s are equivalent to the atomic elements in the complete geographic tabulation lattice. The multilist structure permits the reconstruction of the geographic lattice if desired-hence the properties of lattices may be utilized implicitly with the GTUB.