Editing Geocode (section)

==== Hierarchical naming ====

In the geocode context, [[space partitioning]] is the process of dividing a [[Space#Geographical space|geographical space]] into two or more [[Disjoint sets|disjoint]] [[subset]]s, resulting in a [[Tessellation|mosaic]] of subdivisions. Each subdivision can be partitioned again, [[Recursion|recursively]], resulting in an hierarchical mosaic.

When subdivisions's names are expressed as codes, and code syntax can be decomposed into a parent-child relations, through a well-defined syntactic scheme, the geocode set configures a hierarchical system. A geocode fragment (associated to a subdivision name) can be an abbreviation, numeric or alphanumeric code.

A popular example is the [[ISO 3166-2]] geocode system, representing country names and the names of respective [[Administrative division|administrative subdivisions]] separated by hyphen. For example <code>DE</code> is [[Germany]], a simple geocode, and its subdivisions (illustrated) are <code>DE-BW</code> for [[Baden-Württemberg]], <code>DE-BY</code> for [[Bayern]], ...,  <code>DE-NW</code>  for [[Nordrhein-Westfalen]], etc. The scope is only the first level of the hierarchy. For more levels there are other conventions, like HASC – Hierarchical Administrative Subdivision Codes.<ref>{{cite book|author=Gwillim Law|year=2016|title=Administrative Subdivisions of Countries: A Comprehensive World Reference, 1900 Through 1998|publisher=McFarland |isbn=978-0-7864-0729-3|url-access=registration|url=https://archive.org/details/administrativesu0000lawg}}</ref><ref>{{statoids|id=ihasc|title=Hierarchical administrative subdivision codes}}</ref> The HASC codes are alphabetic and its fragments have constant length (2 letters). Examples:

:<code>DE.NW</code> - [[North Rhine-Westphalia]]. A two-level hierarchical geocode.
:<code>DE.NW.CE</code> - Kreis [[Coesfeld (district)|Coesfeld]]. A 3-level hierarchical geocode.

Two geocodes of a ''hierarchical geocode system'' with same prefix represents different parts of the same location. For instance <code>DE.NW.CE</code> and <code>DE.NW.BN</code> represents geographically interior parts of <code>DE.NW</code>, the common prefix.

Changing the ''subdivision criteria'' we can obtain other hierarchical systems. For example, for [[Drainage basin|hydrological criteria]] there is a geocode system, the US's [[Hydrological code|hydrologic unit code]] (HUC), that is a numeric representation of ''basin names'' in a hierarchical syntax schema (first level illustred). For example, the HUC  <code>17</code> is the identifier of "[[Columbia River drainage basin|Pacific Northwest Columbia basin]]"; HUC <code>1706</code> of "[[Snake River|Lower Snake basin]]", a spatial [[subset]] of HUC <code>17</code> and a superset of <code>17060102</code> ("Imnaha River").