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Explain place_id, i.e. shouldn't be use as permanent id

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marc tobias
2018-11-28 19:36:56 +01:00
parent 121126cb50
commit 1489e6c00e
1 changed files with 28 additions and 4 deletions
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docs/api/Output.md
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@@ -46,7 +46,7 @@ a single place (for reverse) of the following format:
The possible fields are: The possible fields are:
* `place_id` - reference to the Nominatim internal database ID * `place_id` - reference to the Nominatim internal database ID (see notes below)
* `osm_type`, `osm_id` - reference to the OSM object * `osm_type`, `osm_id` - reference to the OSM object
* `boundingbox` - area of corner coordinates * `boundingbox` - area of corner coordinates
* `lat`, `lon` - latitude and longitude of the centroid of the object * `lat`, `lon` - latitude and longitude of the centroid of the object
@@ -75,7 +75,7 @@ a bounding box (`bbox`).
The feature list has the following fields: The feature list has the following fields:
* `place_id` - reference to the Nominatim internal database ID * `place_id` - reference to the Nominatim internal database ID (see notes below)
* `osm_type`, `osm_id` - reference to the OSM object * `osm_type`, `osm_id` - reference to the OSM object
* `category`, `type` - key and value of the main OSM tag * `category`, `type` - key and value of the main OSM tag
* `display_name` - full comma-separated address * `display_name` - full comma-separated address
@@ -148,7 +148,7 @@ attribution to OSM and the original querystring.
The place information can be found in the `result` element. The attributes of that element contain: The place information can be found in the `result` element. The attributes of that element contain:
* `place_id` - reference to the Nominatim internal database ID * `place_id` - reference to the Nominatim internal database ID (see notes below)
* `osm_type`, `osm_id` - reference to the OSM object * `osm_type`, `osm_id` - reference to the OSM object
* `ref` - content of `ref` tag if it exists * `ref` - content of `ref` tag if it exists
* `lat`, `lon` - latitude and longitude of the centroid of the object * `lat`, `lon` - latitude and longitude of the centroid of the object
@@ -203,7 +203,7 @@ generic information about the query:
The place information can be found in the `place` elements, of which there may The place information can be found in the `place` elements, of which there may
be more than one. The attributes of that element contain: be more than one. The attributes of that element contain:
* `place_id` - reference to the Nominatim internal database ID * `place_id` - reference to the Nominatim internal database ID (see notes below)
* `osm_type`, `osm_id` - reference to the OSM object * `osm_type`, `osm_id` - reference to the OSM object
* `ref` - content of `ref` tag if it exists * `ref` - content of `ref` tag if it exists
* `lat`, `lon` - latitude and longitude of the centroid of the object * `lat`, `lon` - latitude and longitude of the centroid of the object
@@ -220,3 +220,27 @@ as subelements with the type of the address part.
Additional information requested with `extratags=1` and `namedetails=1` can Additional information requested with `extratags=1` and `namedetails=1` can
be found in extra elements as sub-element of each place. be found in extra elements as sub-element of each place.
## Notes on field values
### place_id is not a persistent id
The `place_id` is created when a Nominatim database gets installed. A
single place will have a different value on another server or even when
the same data gets re-imported. It's thus not useful to treat it as
permanent for later use.
The combination `osm_type`+`osm_id` is slighly better but remember in
OpenStreetMap mappers can delete, split, recreate places (and those
get a new `osm_id`), there is no link between those old and new id.
Places can also change their meaning without changing their `osm_id`,
e.g. when a restaurant is retagged as supermarket. For a more in-depth
discussion see [Permanent ID](https://wiki.openstreetmap.org/wiki/Permanent_ID).
Nominatim merges some places (e.g. center node of a city with the boundary
relation) so `osm_type`+`osm_id`+`class_name` would be more unique.
### boundingbox
Comma separated list of min latitude, max latitude, min longitude, max longitude.
The whole planet would be `-90,90,-180,180`.