[OSM-talk] Syntactic conventions for tags

[Jochen Topf]

On Thu, Jan 01, 2009 at 11:01:48PM +0000, Andrew Chadwick (mailing lists) wrote:
> People often ask what the various colons, underscores, semicolons and 
> whatnot mean within a tag. The answer is that there are no guidelines, 
> silly; just do what you want! But doesn't mean that de-facto conventions 
> haven't evolved over time anyway, so I've had a go at documenting them. 
> Could someone please review and let me know if I've missed anything 
> important? Better examples would be useful too.
> 
> http://wiki.openstreetmap.org/wiki/Any_tags_you_like#Syntactic_conventions_for_new_tags
> 
> Thanks. I bet you're all doing something completely different.
> 
> (Actually, I like the colon syntax a lot. Wonder if it's worth 
> formalising that a bit more, saying that either order matters, or order 
> doesn't matter?)

Of course the order matters, otherwise its a different tag key. The Venn
diagrams you describe are the wrong image, because sets are unordered.

In most cases a colon is not a sign for a "meta-tag" as you describe there,
but more of a "namespace". This is most often used for external data
attached to imports. See for instance all the keys starting with
"tiger:".

Jochen
-- 
Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298