[Tagging] Wikidata tag

[Dave Sutter]

I really like the idea of linking between OSM and an external database
which contains non-geographic data. I just saw this thread now but I
see a heated discussion has been going on for a while. I think one of
the big benefits of the link is not just identification of on object
(McDonald's) but also the added detail that can be included beyond
what is possible in our tagging scheme, such as the logo or a nice
story about the history or even today's specials (for all those
McDonald's that have a daily special).

I'd like to make one suggestion that I suspect won't go over real
well. But it is a thought people should consider.

There is a natural mechanism for tying information to geographical
locations - the address. There is a particular McDonald's restaurant
in the external database and it will have the postal address 1248
Fairlawn Ave, Morgantown, WV, USA. This connects it to the OSM
database.

This address concept extends beyond postal addresses. The "ref" tag
should be used for this purpose. For example, a transit route should
have a reference to say what route it is. This should be the publicly
available name for the route which is also used in the external
database.

There are many other ref values that serve as addresses - Gate 7 in an
airport. Room 325 in a building. Exit 12 on a highway. Aisle 5 Shelf 2
Bin A in a grocery store. The list is endless. Back to the McDonald's
case, in addition to address I am sure there is a franchise number.
And there is the Value Added Tax ID which was mentioned (which I have
never heard of).

Admittedly we may need to improve our ref tagging to make sure it is
adequate to specify objects in this manner. And some of these ref
values will be difficult to get.  Most notably this method would
require the value be set in two places, OpenStreetMap and the external
database. But the benefit is that the value selected is a meaningful
value in its own right, not just within the context of a single
external database. These values were defined before OpenStreetMap or
the external database came along. And they allow linking between
OpenStreetMap and any number of external databases. That may be the
biggest benefit.

Dave