On 3/10/22 22:01, Peter Elderson wrote:
I would avoid "primary key", because that is a term from database
management systems. It means the identifying attribute (Id) of an
entity, usually a unique identifier with an index (primary index),
used to retrieve records and to link the entity (table) to other
tables. Something else entirely.
Main key is better.
Further: the main key gives the type of object, the main tag gives a
category within that type of object. That is an important difference,
in documentation.
semantics (nit picking) An OSM 'tag' is both a key and a value, example
{{tag|colour|yellow}}. So it gives both 'object' and 'category'. Ok?
Feature tag, I think it means the tag that gives the object type (the
main key) and the category within the object type (the value). So,
equivalent to main tag.
I think the term secondary tag(s) and secondary key(s) are often used
for the extra attributes of a feature, implying there should be a main
tag first, to give the secondary tags meaning.
If we use 'main key'/'main tag' then secondary key/tag is logical.
Peter Elderson
Op ma 3 okt. 2022 om 12:40 schreef martianfreeloader
<[email protected]>:
Thank you all for the many insightful replies to my question!
What I've learnt so far:
1) A feature is something in the physical world. This is well
documented
in the wiki: https://wiki.openstreetmap.org/wiki/Features
2) There is no such thing as a "primary feature".
3) The terms "main key", "primary key" and "feature tag" are
synonymous,
except for the tag/key distinction.
4) None of the above terms is official OSM terminology.
5) None of these terms is well documented in the wiki.
-------
It looks like a couple of things would be good to get done:
A) We should get rid of the term "primary feature" in the wiki page
https://wiki.openstreetmap.org/wiki/Map_features
B) It would be useful if we agree on *one* official term for "main
key",
"primary key" or "feature tag". (I think "primary key/tag" is the
most
popular one)
C) We should document what we mean by this.
------
Open questions:
Q1) Which term should we choose as official term? ("main
key"/"primary
key"/"feature tag")
Q2) Should one OSM object hold multiple "primary tags"? (ongoing
discussion between Mateusz, Martin, Warin, Marc et al.)
On 03/10/2022 12:16, Marc_marc wrote:
> Le 03.10.22 à 10:47, Mateusz Konieczny via Tagging a écrit :
>> there are cases where road is going in stream bed
>
> imho only one main feature/objet : the stream bed
> and car use it, a bit like a bicycle uses a road.
>
> but we don't really have a secondary tag to say that
> the stream bed is usable by a car... so we end up
> describing this secondary use with a 2nd main tag...
> this is not perfect
>
>
>
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