[OSM-talk] osm2pgsql hstore (was: Wind turbines no longer rendered on mapnik layer)
jochen at remote.org
Thu Feb 16 23:00:04 GMT 2012
On Thu, Feb 16, 2012 at 06:25:30PM +0000, Graham Jones wrote:
> <grumble> Why create a key generator:power_source rather than just use
> power_source. power_source is much more generic so you could re-cycle it
> for things like district heating, but generator:power_source is only ever
> going to be used for generating stations, and needs a new column in the
> database. </grumble>. I think I just prefer more generic, re-usable keys
> rather than trying to invent a new one for each situation....
Generic key names can be confusing, especially when one OSM object is used for
multiple things. Say there is a way tagged as railway and at the same time this
way is part of an area tagged as a generating station. Does "power_source" mean
the type of generating station or the type of power used by the railway
(overhead vs. third rail vs. unelectrified)? I hope this example is
hypothetical, but people do strange things in OSM...
Non-generic tags also make tools such as Taginfo more useful, because each tag
stands on its own. They make it immediately clear if the tagging is incomplete.
If the "generator" tag got lost, how do we know what the "power_source" tag
is supposed to mean?
So on the one side you have generic tags like "type" and "class" and "id" which
are very confusing. You never know what they belong to. On the other side you
have rather complex tagging schemas like in your generator:... example. Thats
sometimes hard to use, too. We still have to figure out where the sweet spot is,
but I tend to prefer the more explicit keys.
Jochen Topf jochen at remote.org http://www.remote.org/jochen/ +49-721-388298
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