If you search for an airport (aeroway=aerodrome) around brescia, italy, you will also receive a hit for a military airfield, which happens to be tagged as an aerodrome also (it's taggged: aeroway=aerodrome, landuse=military, military=airfield). To avoid this I want to search for aeroway=aerodrome but exclude [military]. I've tried [! military] and [military~"^$"]. Any suggestions?
This particular case may be rare, I realize, but the concept of negating multi-classed elements is useful. And multi-classed elements is not a rare occurance. In general, they seem to be complimentary, not conflicting, so it's not an issue. I also realize that I can weed out conflicting hits with some back-end processing. I wasn't expecting a military airfield to appear with a commercial aerodrome.
In any case, here is a shortened version of my query. I include node, way and relation in full query:
http://overpass-api.de/api/interpreter?
data=[out:json][timeout:25][bbox:45.400861,9.868469,45.641408,10.542755];
(node[aeroway~%22aero|term|heli%22][! military]; ... ) out etc
or:
http://overpass-api.de/api/interpreter?
data=[out:json][timeout:25][bbox:45.400861,9.868469,45.641408,10.542755];
(node[aeroway~%22aero|term|heli%22][military~%22^$%22]; ... ) out etc
If you try to run it, you'll need to include way and relation. Also, as you can see I don't exactly ask for aeroway=aerodrome. I include terminal and variations on heliport. My experience has been that some aerodromes are tagged only as "terminal", so if you're looking for an airport, asking for "aerodrome" isn't enough.
The correct syntax for negation is as follows:
[military !~ ".*"]
Please see the documentation on the OSM wiki for details.