[Tagging] Map maintenance with StreetComplete - Preferred tagging

Tobias Zwick osm at westnordost.de
Sat Jul 25 13:53:18 UTC 2020

> It is completely possible to add this functionality to the API in a
> backwards compatible fashion, at the cost of a long per tag in the
> current table (assuming that we don't need the information for historic
> object versions, so at a reasonable cost space wise. There are a couple
> of semantic issues that need to be considered but definitely not rocket
> science. Where the big effort is likely adapting the internal tools
> (database dumps etc), cgi-map and in the end migrating the database.
> If I can find some time over the next months I might prototype this, but
> if somebody can do it earlier pls be my guest.

I am happy that through this topic, the topic of API support for
recording and getting the last checked date gained traction (again).

We,... well, we probably could, but we shouldn't always rely on tags
like check_date etc.. As Mateusz Konieczny rightfully noted in another
branch, meta-tags as opposed to API support has the potential to become
out of date if successive editors forget to update the check_date tag
when they update the object or tag it is referring to.

So, all the more I say it is pretty awesome that you plan to conceive a
plan for this. Whatever comes out of it, in any case thank you for
taking an initiative, Simon!
Such a feature would also open up much more room for comprehensive
analyzing and QA tools focussed on map maintenance, a topic that is or
at least is becoming more and more important in my opinion. The
endorsements there were so far for the map maintenance in StreetComplete
indicate that the topic has become to take precedence in the minds of
many mappers, also of those usually not that involved in discussions in
the established channels.

Regarding changes to the API, it would then probably look like this?

<node ... >
  <tag ...

Thinking a little bit about it, it would not be a 1:1 replacement of
some_tag:check_date=2019-09-04 because check_date is usually used for
when something has been checked on-site (survey). A timestamp on a tag
just records "a" change. That could have been a mechanical edit, like
for example the recent change of http:// urls to https:// urls where
possible. Though I guess this would be good enough, it may be worth a
thought whether to also include the source field of the linked changeset
in the tag xml.

I reckon a difficulty for implementing something like this would be the
issue of "touching" elements in order to update their timestamp. I think
this may be possible already with the current API, but what is really
missing would be the possibility to "touch" certain tags only - only the
tags that one checked but didn't change because there was no change


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