[OSM-talk] [Talk-us] Role of the Wiki

Martin Koppenhoefer dieterdreist at gmail.com
Wed Dec 5 17:53:27 GMT 2012


2012/12/5 Serge Wroclawski <emacsen at gmail.com>:
> On Tue, Dec 4, 2012 at 8:44 PM, Jeff Meyer <jeff at gwhat.org> wrote:
>> - For relations: do NOT read the wiki & HELL YES read the wiki
> Relations are a complex topic. They're generally loved by those who
> like to talk in theory but not in practice.
> The problem is they're very hard to work with.


the thing with relations is, they are completely universal, you can
model any kind of relation between nodes, ways and other relations,
but naturally only a few concepts are generally evaluated (and used in
mapping). Some relations are established though, and those get also
evaluated for a wider group of maps, are supported in current tools
and libs like osmium or osm2pgsql or for routing, and it's worth
mentioning this.

These are
- "multipolygon" and "boundary" relations (basically the same)
- "route" relations
- turn "restriction" relations

to see more types and actual usage statistics have a look at taginfo:
http://taginfo.openstreetmap.org/keys/type#values
(there is public_transport, site, street and associatedStreet also in
significant numbers, but AFAIK they get less often evaluated). Note
that not all objects with a "type"-tag are relations.

cheers,
Martin



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