[Tagging] Adding values to usage=* key for power transmission
sommerluk at gmail.com
Wed Dec 17 08:19:51 UTC 2014
2014-12-16 23:42 GMT+01:00 François Lacombe <fl.infosreseaux at gmail.com>:
>> I think there is a big difference between "operator" and "usage": the latter
>> is most probably intended to be a formal tag with a limited, well defined
>> set of values, while the former is a free text field with any value possible.
>> Mixing up "usage" in different contexts makes life harder for documentation,
>> taginfo users, etc.
>> Adding context by applying a namespace would help.
> All keys in OSM are supposed to have free-text values. Let's start to consider
> this question widely and tags as a whole. Not only for power, railway, usage
> or operators.
> The wiki gives information about which are most commonly encountered together.
> If tools aren't able to deal with this, they should be improved.
No. Tools do NOT have to be improved. Keys like “usage” need
definitively a closed list of accepted values – with a well-defined
meaning. If they do not have it, they are almost useless for data
Imagine if we would consider the highway=* tag for streets as a
free-text value. You could find values like “motorway”, but maybe also
“freeway” with the same meaning, and in France maybe “autoroute”.
Other people may use “metered freeway” or something else. It would be
impossible for any software to order and interpret all this data. A
processing software is just a “stupid” computer program; it can’t
interpret things the same way like an intelligent human is able to do.
You want to have the usage key to make a difference between different
usages. For example, if all cables for street lightning have
usage=lightning and all cables for distribution have
usage=distribution, you can make special maps for street lightning.
Moreover, you can make special maps for the distribution network.
However, if some people use “street_lightning”, others “lightning” and
other “light” and others “lamps”, the key will be useless for
software. You cannot do a different rendering based on the key.
We need definitively a closed list of correct values for this – with a
well-documented meaning for each value. (By the way, the railway
people do the same for “usage”). That does not mean that we cannot
make longer the list in the future. However, usage=* cannot be
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