[OSM-dev] Multiple values "warning" in P2

Richard Fairhurst richard at systemed.net
Thu Jul 26 09:42:19 BST 2012

Alan Mintz wrote:
> Semi-colons are the agreed-upon way to provide multiple values for a 
> field. It seems wrong to "warn" of their use, especially given the 
> demonstrated potential to cause users to "fix" such values incorrectly.

In most cases having two values in a field is undesirable. Virtually no data
consumers will correctly parse them: if you have a node with
amenity=pub;cafe, it will generally not be recognised as either a pub or a

P2 does have a small whitelist of tags for which it won't warn about a
semicolon and I'm happy to consider adding to that, if you have a particular

I suspect however that what you're really talking about is the ref tag and
that's a little more complex. In some countries (such as, I think, Britain,
France and Germany) then a road genuinely can't have two numbers (excepting
E-roads); in some it can (US, Poland). So at the least any solution here
will need to be bbox-specific.

But I'd welcome opinions (ideally on tagging@, not here) about whether this
is indeed the way to go. Are route relations not a better solution for those
places where roads regularly have two numbers? Would we not be better off
fixing our osm2pgsql/Mapnik setup to render refs from relations, rather than
telling P2 not to warn about, essentially, deprecated behaviour?


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