cache all postcodes

[nominatim.git] / docs / develop / Ranking.md

diff --git a/docs/develop/Ranking.md b/docs/develop/Ranking.md
index 278039db6c923c4ab4db46b64f70d75c61ef41e6..5b1ca1915ca653624261278c04adffa65cbc9882 100644 (file)
--- a/docs/develop/Ranking.md
+++ b/docs/develop/Ranking.md
@@ -7,7 +7,7 @@ different purposes, which are explained in this chapter.
 ## Search rank
 
 The search rank describes the extent and importance of a place. It is used
-when ranking search result. Simply put, if there are two results for a
+when ranking search results. Simply put, if there are two results for a
 search query which are otherwise equal, then the result with the _lower_
 search rank will be appear higher in the result list.
 
@@ -23,7 +23,7 @@ rank   | typical place types             | extent
 4      | countries                       | -
 5-9    | states, regions, provinces      | -
 10-12  | counties                        | -
-13-16  | cities, municipalities, islands | 7.5 km
+13-16  | cities, municipalities, islands | 15 km
 17-18  | towns, boroughs                 | 4 km
 19     | villages, suburbs               | 2 km
 20     | hamlets, farms, neighbourhoods  |  1 km
@@ -51,16 +51,24 @@ The following table gives an overview how ranks are mapped to address parts:
  10-12       | county
  13-16       | city
  17-21       | suburb
- 22-25       | neighbourhood
+ 22-24       | neighbourhood
+ 25          | squares, farms, localities
  26-27       | street
  28-30       | POI/house number
 
 The country rank 4 usually doesn't show up in the address parts of an object.
 The country is determined indirectly from the country code.
 
-Ranks 5-25 can be assigned more or less freely. They make up the major part
+Ranks 5-24 can be assigned more or less freely. They make up the major part
 of the address.
 
+Rank 25 is also an addressing rank but it is special because while it can be
+the parent to a POI with an addr:place of the same name, it cannot be a parent
+to streets. Use it for place features that are technically on the same level
+as a street (e.g. squares, city blocks) or for places that should not normally
+appear in an address unless explicitly tagged so (e.g place=locality which
+should be uninhabited and as such not addressable).
+
 The street ranks 26 and 27 are handled slightly differently. Only one object
 from these ranks shows up in an address.
 
@@ -79,9 +87,9 @@ into the database. There are a few hard-coded rules for the assignment:
     * highway nodes
     * landuse that is not an area
 
-Other than that, the ranks can be freely assigned via the JSON file
-defined with `CONST_Address_Level_Config` according to their type and
-the country they are in.
+Other than that, the ranks can be freely assigned via the JSON file according
+to their type and the country they are in. The name of the config file to be
+used can be changed with the setting `NOMINATIM_ADDRESS_LEVEL_CONFIG`.
 
 The address level configuration must consist of an array of configuration
 entries, each containing a tag definition and an optional country array: