When you search http://nominatim.openstreetmap.org the details page shows a lot of information and some are missing when querying nominatim.
For example when I search for "choisy" : http:/nominatim.openstreetmap.org/search?format=xml&limit=5&addressdetails=1&q=choisy
(I removed a slash of http:// because I'm not allowed to post 2 links ...)
Result on nominatim : http://nominatim.openstreetmap.org/details.php?place_id=158972963
Result I get with the httprequest is the following:
It's missing (from the "Address" table on the page) in my returned XML result.
"Haute-Savoie boundary:administrative relation 7407 6 0"
Do you know how to get it ?