[Tagging] Map maintenance with StreetComplete - Preferred tagging

Jmapb jmapb at gmx.com
Sat Jul 25 01:28:16 UTC 2020

On 7/24/2020 7:12 PM, Cj Malone wrote:

>> OSM does not store edit timestamps for individual tags, only for the
>> object as a whole. Finding out when a tag was changed requires a
>> review of the entire history. I had to do this once when I saw a
>> clear highway=motorway_link tagged as highway=motorway, with me as
>> the last user to edit that road segment. Turns out the original
>> mapper was the one to make the tagging mistake, not yours truly, but
>> I only found this once reviewing the history.
> Yeah, that option would require a new API and work done on the OSM
> server to both calculate the last time a tag was edited, serve it and
> store the timestamp when "touched" or updated. But once that's done
> it's done for multiple clients, not just StreetComplete.
> Otherwise StreetComplete would need to use the History API one each
> individual nwr and try to calculate the age of a tag.

It sounds to me like what you're describing would require not just a new
API but a change to the database schema to add a datetime field to each
tag. Otherwise there would be no way to encode the timestamp of the
confirmation of an existing tag that does not need changing. The history
API will only tell you when tags change. The tag validation from the
wizard you described two posts above -- there's no way to record that
validation. Except maybe to shoehorn it into the info tags on the
changeset itself.

My preference is to avoid updating a element if all info is complete and
nothing has changed. I suppose a single datetime field for last survey
might be workable, but I fear it will lead to giant bogus "survey"
changesets changing nothing but the "last survey" field. I don't think
the field would ultimately be trustworthy because it isn't verifiable.


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