[Talk-GB] OSM UK address project: tags

[Mark Goodge]

On 22/12/2021 10:28, Colin Smale wrote:

> What's so bad about adopting the RM model? Given the huge levels of 
> "tradition" in UK addressing (particularly in rural areas) they had a 
> big challenge to come up with a data model that would accommodate all 
> the quirks while providing an efficient way of uniquely identifying a 
> delivery point for post. We are not going to a better job than they have 
> done. Are we just being stubborn?

I agree. The format of a postal address is the same no matter whether 
the item is delivered by Royal Mail, Amazon or DPD. When people think of 
an address, what they are thinking of is what you'd put on a letter. We 
shouldn't be trying to reinvent the wheel here.

That said, because of the way that OSM's data is structured (unlike the 
PAF, it isn't a flat file), we aren't tied to RM's structure in cases 
where it's clear that our tags can give more useful information. A 
specific example of that is a house I used to live in, which has a 
postal address of

Flacks Farm
43 Sedge Fen
Lakenheath
Brandon
Suffolk
IP27 9LG

Written like that, it looks like a standard postal address. The quirk is 
that Sedge Fen is not a street - instead, it's a rural hamlet comprising 
several unnamed roads. So addr:street would be the wrong tag here. The 
question is, which would be correct? Personally, I'd tag it like this:

addr:housename "Flacks Farm"
addr:housenumber "43"
addr:hamlet "Sedge Fen"
addr:village "Lakenheath"
addr:post_town "Brandon"
addr:county "Suffolk"
addr:postcode "IP27 9lG"

That has the advantage of both being literally correct, from a 
geographic perspective, as well as converting easily into a written 
address if you simply take it in hierarchical order (in particular, 
knowing that hamlet < village < post town). The disadvantage is that it 
uses tags which aren't that well understood, and often conflict with 
common addressing conventions. An alternative, which also works from an 
addressing perspective, would be:

addr:housename "Flacks Farm"
addr:housenumber "43"
addr:place "Sedge Fen"
addr:town "Lakenheath"
addr:post_town "Brandon"
addr:county "Suffolk"
addr:postcode "IP27 9lG"

That uses "town" for Lakenheath, which, despite being administratively 
incorrect (Lakenheath is a village, not a town) is consistent with 
common addressing usage of having "town" for the settlement name 
irrespective of legal identity, and "place" for the hamlet, which is 
consistent with the wiki and, it seems common usage in OSM. And, again, 
this resolves easily to a written address just by following the hierarchy.

The key to both of these, though, is distinguishing addr:town from 
addr:post_town. And I'm a little surprised that the latter seems to be 
so infrequently used in OSM (only 11 objects, according to a taginfo 
search). I think this is something that really does need to be prominent 
in the wiki, with a clear explanation of the difference and mappers 
encouraged to use addr:post_town correctly. Essentially, addr:town 
should be used for the settlement that the object is actually in (or 
administratively part of, for rural areas that are part of the curtilage 
of a settlement), while addr:post_town should be used (and only used) 
where the postal address includes a specified post town that is 
different to the name of that settlement.

Mark