Von: "Sergio Manzi" <s...@smz.it>
An: tagging@openstreetmap.org
Betreff: Re: [Tagging] Benefits of namespaces
François,
The discussion about this has also been brought to the forum, here: https://forum.openstreetmap.org/viewtopic.php?id=64825
I'm unsure if it is better to continue it here in the ML, there in the forum, or in both places...
Le mer. 19 déc. 2018 à 22:26, Richard <ricoz....@gmail.com> a écrit :the OSM tag chain should be imho used only for very common things because each member
of the chain will turn up as a "top level" tag in the database and taginfo.We are using such chains in Power, Pipeline and Telecom groups. It works well :power=transformer + transformer=distribution + voltage:primary=20000 + voltage:secondary=400man_made=street_cabinet + street_cabinet=telecom + telecom=exchange + telecom:medium=copper + operator=Orange
"Transformers" is a perfect example of "namespacing done backward". Why "voltage:secondary=220"? In a correctly namespaced world it would be "secondary:voltage=220".
I understand that in spoken English you can say "the voltage of the secondary is 220 Volt", and that's probably why those keys have been built with the terms in that particular order. (BTW, logic and wording is very different in different cultures and languages. I think it wouldn't had been in that order in, say, German: can a german speaker please confirm that?)Transformers can have and very often have more than one secondary: you have dealt with that using things like "voltage:tertiary=*" and the likes (windings:tertiary=*, I suppose...). And what if the transformer has 3 secondaries? Or 4?
Isn't "secondary:1:voltage=200" better? Don't you see that's more logical and expandable? Don't you see that here we assign a quantity (220) to something that has the correct dimensions (voltage), like in the previously globally defined key "voltage=*"? Don't you see how with that syntax everything related to the first (second, third, fourth,... nth) secondary (wingdings, current, whatever...) would be grouped under "secondary:n:*="?
And if transformers weren't meant to be a "namespaced thing", why using the columns? Why not voltage_secondary=* ?
Don't you see that with the transformers a new first level keyword, "rating=*" have been implicitly defined and documented in the transformers page and how that keyword can be useful in other contexts... or namespaces, if you prefer?
BTW, what is that telecom:medium=copper thing (https://wiki.openstreetmap.org/wiki/Key:telecom:medium)? "Telecoms" do not have a medium: local loops have. Is that meant to be a namespaced thing? Have this being debated/approved? I have seen it applied to buildings: what is the meaning of that?
Adding power: and telecom: prefixes would be seriously bad to encourage for contribution and extremely redundant.
To the contrary! Please read in the forum my rationale explaining exactly how that would be beneficial...
Furthermore, refining of well used tags often get discouraged because of their usage.This dosn't include the redundancy in namespaces' prefixes which is worse.If used extensively for attributes I would consider it polution of the database.
It is also much less flexible as you can specify only one attribute at a time.If you have to define more than one attribute with the same name it may be the attribute isn't weel defined.Have you examples please?All the bestFrançois
Sorry, I'm really now on the verge (less than 24 hours...) of a small journey, so I would probably be unable to answer/contribute anymore until January, 6.
Cheers,
Sergio
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