A few weeks back I gave two talks at the State Of The Map 2013 conference. One about Osmium, the other called “Towards an Area Datatype for OSM”. The slides and videos from both talks are now available on my talks page. Thanks to Peter Barth for “liberating” the videos from the 8 hour long flash-only videos put up originally.

OpenStreetMap doesn’t allow multiple tags with the same tag key. But there is a believe out there in OSM land, that you can work around this by putting all the tag values you want into one tag using semicolons as separator characters. So if there is a bank with an ATM machine, people tag [amenity=bank;atm]. Or there is a road with several refs, then they tag them as [ref=I 70;US 40] and hope that it will magically work. And it does work in some cases. But in many cases it doesn’t. Let’s look into this a bit.