So I did what I had planned in the previous diary and checked with some Overpass queries. For example, this query should probably produce no result.

Tests

Now, the following Overpass requests work:

• Get the subway network in Seoul (lines 1 to 9) (see on a map):

    https://wiki.openstreetmap.org/wiki/Tag:relation[route=subway][name~"^[1-9]"]({{bbox}});
    (._;>);
    out;
  

• Get all stops on line 2 (see on a map or get the data)

    https://wiki.openstreetmap.org/wiki/Tag:relation[route=subway][name~"^2"]({{bbox}});
    node(r:"stop");
    out;
  

Conclusions

I have 3 conclusions.

1. I used the old public transport scheme, aka version 1, except where I had already added https://wiki.openstreetmap.org/wiki/Tag:public_transport=stop_position nodes. Therefore everything is not harmonized: in subway route relations, the stop role is associated sometimes with a https://wiki.openstreetmap.org/wiki/Tag:railway=station node, sometimes with a https://wiki.openstreetmap.org/wiki/Tag:public_transport=stop_position node (but only to one node in every subway station for each line).

   Maybe I should have removed all https://wiki.openstreetmap.org/wiki/Tag:public_transport=stop_position tags and kept only https://wiki.openstreetmap.org/wiki/Tag:railway=station nodes. The https://wiki.openstreetmap.org/wiki/Tag:public_station=stop_position tag on railways does not seem very useful unless you are ready to really map the station according to the new Public Transportation scheme, i.e. add the https://wiki.openstreetmap.org/wiki/Tag:public_transport:version=2 tag on the route relation in JOSM. Version 2 might let client software design very precise pedestrian routing (such as what Naver Maps does very well in Korea), but that requires very high quality data. It does not seem realistic in Seoul which has a very small OSM contributor community compared to other large cities (which makes contributing more fun than in other cities like Paris where you have almost nothing to map any more, except shops).

   Therefore it is probably better to be modest and keep with the old schema (https://wiki.openstreetmap.org/wiki/Tag:public_transport:version=1): add https://wiki.openstreetmap.org/wiki/Tag:railway=station nodes to the route relations with role stop and that’s all, except maybe for a couple of subway stations in my neighborhood.

   However, using several relations for branches (e.g. on line 5) is a good thing, but that can also be done with version 1.

2. JOSM is a good piece of software.

3. JOSM is a very good piece of software. The more I am exploring its advanced features (layers and filters, this time), the more I am amazed how well it is adapted to the (experienced) user.