[Tagging] Comparison of tag support: Mapnik, Osmarender, Potlatch, JOSM, Kosmos, Map Features (wiki)

Tobias Knerr osm at tobias-knerr.de
Sun Dec 13 14:25:52 GMT 2009

Steve Bennett wrote:
> http://wiki.openstreetmap.org/wiki/User:Stevage/tagsupport
> This is getting interesting. Side by side are now Mapnik, Osmarender,
> Potlatch, JOSM, Kosmos, and the Map Features wiki page.

That's an interesting table, thanks. :)

> The number of redlinks
> (undocumented tags) is also somewhat alarming

The majority of redlinks are tags that are composed from a set of
possible keys and possible values that can be arbitrarily combined.

For example, the
{bicycle, hgv, horse, motor_vehicle, ...}
x {no, permissive, private, yes, destination}
{abandoned, construction, dismantled, disused, ...}
x {bridleway, byway, cycleroad, cycleway, ...}
sets of tags easily generate hundreds of combinations.

A lot of the others are keys where the key page will also define the
values possible for it (such as bridge=*, parking=* etc.), but there
aren't pages for the individual values.

In both cases, I don't think creating a wiki page for each key-value
pair would make any sense. Keeping redirects up to date manually
wouldn't be easy, either. Maybe this could be automated, though.

> - we should get into the
> practice of documenting every tag, regardless of whether it has any
> "official" status.

I don't think we should care for tags which aren't documented anywhere
and /aren't really being used/ either, just because the person inventing
them had write access to a renderer style sheet. Actually, it would be
nice to have tag usage statistics from tagwatch or osmdoc in the table,
too - this would quickly tell the reader whether, for example,
"small_town" has any relevant support by mappers (hint: it hasn't).

> Your comments welcome!

I notice that your Map Features parsing has split the "24/7" value for
opening_hours. I'm not sure whether similar cases occur elsewhere, too.

Tobias Knerr

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