+## Configuring the Import
+
+Which OSM objects are added to the database and which of the tags are used
+can be configured via the import style configuration file. This
+is a JSON file which contains a list of rules which are matched against every
+tag of every object and then assign the tag its specific role.
+
+The style to use is given by the `NOMINATIM_IMPORT_STYLE` configuration
+option. There are a number of default styles, which are explained in detail
+in the [Import section](../admin/Import/#filtering-imported-data). These
+standard styles may be reference by their name.
+
+You can also create your own custom syle. Put the style file into your
+project directory and then set `NOMINATIM_IMPORT_STYLE` to the name of the file.
+It is always recommended to start with one of the standard styles and customize
+those. You find the standard styles under the name `import-<stylename>.style`
+in the standard Nominatim configuration path (usually `/etc/nominatim` or
+`/usr/local/etc/nominatim`).
+
+The remainder of the page describes the format of the file.
+
+### Configuration Rules
+
+A single rule looks like this:
+
+```json
+{
+ "keys" : ["key1", "key2", ...],
+ "values" : {
+ "value1" : "prop",
+ "value2" : "prop1,prop2"
+ }
+}
+```
+
+A rule first defines a list of keys to apply the rule to. This is always a list
+of strings. The string may have four forms. An empty string matches against
+any key. A string that ends in an asterisk `*` is a prefix match and accordingly
+matches against any key that starts with the given string (minus the `*`). A
+suffix match can be defined similarly with a string that starts with a `*`. Any
+other string constitutes an exact match.
+
+The second part of the rules defines a list of values and the properties that
+apply to a successful match. Value strings may be either empty, which
+means that they match any value, or describe an exact match. Prefix
+or suffix matching of values is not possible.
+
+For a rule to match, it has to find a valid combination of keys and values. The
+resulting property is that of the matched values.
+
+The rules in a configuration file are processed sequentially and the first
+match for each tag wins.
+
+A rule where key and value are the empty string is special. This defines the
+fallback when none of the rules match. The fallback is always used as a last
+resort when nothing else matches, no matter where the rule appears in the file.
+Defining multiple fallback rules is not allowed. What happens in this case,
+is undefined.
+
+### Tag Properties
+
+One or more of the following properties may be given for each tag:
+
+* `main`
+
+ A principal tag. A new row will be added for the object with key and value
+ as `class` and `type`.
+
+* `with_name`
+
+ When the tag is a principal tag (`main` property set): only really add a new
+ row, if there is any name tag found (a reference tag is not sufficient, see
+ below).
+
+* `with_name_key`
+
+ When the tag is a principal tag (`main` property set): only really add a new
+ row, if there is also a name tag that matches the key of the principal tag.
+ For example, if the main tag is `bridge=yes`, then it will only be added as
+ an extra row, if there is a tag `bridge:name[:XXX]` for the same object.
+ If this property is set, all other names that are not domain-specific are
+ ignored.
+
+* `fallback`
+
+ When the tag is a principal tag (`main` property set): only really add a new
+ row, when no other principal tags for this object have been found. Only one
+ fallback tag can win for an object.
+
+* `operator`
+
+ When the tag is a principal tag (`main` property set): also include the
+ `operator` tag in the list of names. This is a special construct for an
+ out-dated tagging practise in OSM. Fuel stations and chain restaurants
+ in particular used to have the name of the chain tagged as `operator`.
+ These days the chain can be more commonly found in the `brand` tag but
+ there is still enough old data around to warrant this special case.
+
+* `name`
+
+ Add tag to the list of names.
+
+* `ref`
+
+ Add tag to the list of names as a reference. At the moment this only means
+ that the object is not considered to be named for `with_name`.
+
+* `address`
+
+ Add tag to the list of address tags. If the tag starts with `addr:` or
+ `is_in:`, then this prefix is cut off before adding it to the list.
+
+* `postcode`
+
+ Add the value as a postcode to the address tags. If multiple tags are
+ candidate for postcodes, one wins out and the others are dropped.
+
+* `country`
+
+ Add the value as a country code to the address tags. The value must be a
+ two letter country code, otherwise it is ignored. If there are multiple
+ tags that match, then one wins out and the others are dropped.
+
+* `house`
+
+ If no principle tags can be found for the object, still add the object with
+ `class`=`place` and `type`=`house`. Use this for address nodes that have no
+ other function.
+
+* `interpolation`
+
+ Add this object as an address interpolation (appears as `class`=`place` and
+ `type`=`houses` in the database).
+
+* `extra`
+
+ Add tag to the list of extra tags.
+
+* `skip`
+
+ Skip the tag completely. Useful when a custom default fallback is defined
+ or to define exceptions to rules.
+
+A rule can define as many of these properties for one match as it likes. For
+example, if the property is `"main,extra"` then the tag will open a new row
+but also have the tag appear in the list of extra tags.
+
+### Changing the Style of Existing Databases
+
+There is normally no issue changing the style of a database that is already
+imported and now kept up-to-date with change files. Just be aware that any
+change in the style applies to updates only. If you want to change the data
+that is already in the database, then a reimport is necessary.
projects / nominatim.git / commitdiff