[Imports] Belgium address import

[Pieren]

In France, we "import" addresses since ~2010. I can provide some feedbacks here:

- "address on building vs node" : we see two camps here although a
majority seems to agree that on densified urban zones, the node model
is better because it is easier for multiple addresses on the same
building and your routing software will be more accurate even if the
node is not "exactly" at the entrance point. Think that "one address
per building" and "one building per address" is not valid in many,
many cases.

- "proliferation of address schemes" : I know only 2 models, the one
with all "addr:" tags repeated on the element and the one with the
relation "associatedStreet". Again, we have two camps in France,
irreconcilable this time, where some contributors prefer the relation.
I made recently some stats in France and it seems that both models are
co-existing (~50-50%) and in some rare places, there are even both
used together (mainly because some applications don't recognize the
relation "associatedStreet"). I will not argue for one model or the
other since both have advantages and disadvantages, as usual in OSM. I
personnally stoped worrying about this since both can work and it's
even possible to swap from one model to the other. But what I like is
that contributors have the choice. Nobody should be "enforced" to
adopt one scheme. Sounds scary in the OSM environment. Where we have a
consensus is to not duplicate some tags like "addr:country" or
"addr:city". The postcode is another subject and is probably a more
country specific subject (in some areas, the postcode is related to an
administrative boundary, sometimes it's completely unrelated or hard
to define by polygons, etc). Postcode will probably need a better
standardization in OSM in the future but today, we accept to duplicate
it when it's not possible to define it in the admin boundary.

- "addresses before buildings" : it sounds easier to add addresses on
buildings than the opposite but is it really true ? I cannot see who
is enough authoritative in OSM to decide mapping priorities. Some
people like to see their bicycle path first because they use OSM for
their bike routes. Other people are fully concentrated on mapping
power lines first, before roads, before landuse's. Why not. Who am I
to decide what has to be mapped first ?

- "address is a feature or an attribut" : the question was already
raised in the past without a clear answer. It seems that many people -
or even applications - do not
 care about addresses as a feature and they like to duplicate the same
address on all the POI they add into the same building. So when I read
that conflation should avoid duplicates, I'm unconvinced because
duplicates will come back later, anyway.

- it was not mentionned here but OSMI is providing a nice QA tool for
addresses ([1]).

Pieren

[1] http://tools.geofabrik.de/osmi/?view=addresses&lon=2.36419&lat=48.85332&zoom=16&opacity=0.58&overlays=buildings,buildings_with_addresses,postal_code,nodes_with_addresses_defined,nodes_with_addresses_interpolated,no_addr_street,street_not_found,interpolation,interpolation_errors,connection_lines,nearest_points,nearest_roads