[Talk-GB] OSM UK address project: tags

[Mark Goodge]

On 22/12/2021 12:31, Simon Poole wrote:
> 
> Am 22.12.2021 um 12:13 schrieb Mark Goodge:
>> ...
>> 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.
>> ...
> 
> 
> The definition of addr:city -is- "The name of the city as given in 
> postal addresses of the building/area." straight from the wikis mouth, 
> aka the postal town or whatever the equivalent is.

Yes, but that's factually wrong, at least in the UK, and the wiki is 
wrong here. A city is not necessarily the same as a postal town, and 
shouldn't be used interchangeably. Doing so adds ambiguity to the data 
which is both unnecessary and avoidable.

For example, as a data consumer, suppose I wanted to extract a list of 
all the pubs in Stoke-on-Trent. The most obvious way of doing that is to 
look for everything that's tagged as amenity=pub and 
addr:city=Stoke-on-Trent. But, if people are using city as a synonym for 
post town, that won't just give me pubs in Stoke, it will also give me 
pubs in all the small towns and villages around Stoke. That would be 
wrong, and it would be caused by a wrong use of the addr:city tag. 
Separating the geographic concept of a city from the address concept of 
a post town avoids that ambiguity.

More generally, the use of city as a synonym for "urban area" in address 
databases is very much an Americanism, and doesn't map onto British (and 
much European) usage where the term "city" has a defined legal meaning. 
It also doesn't match how the average British user of address data 
perceives the term "city", or how it's used by postal delivery 
organisations (including, but not limited to, Royal Mail).

If the point of this project is to collect address data for the UK, then 
we need to collect the data in the format that a typical British user 
(and contributor) of the data would use. Otherwise, we're just setting 
ourselves up for a whole world of pain caused by some data contributors 
reading the wiki and using OSM-specific tags while others just use the 
tags which reflect the terminology they would use in everyday life. The 
best way to avoid that is for the wiki to follow typical UK conventions.

Mark