<div dir="ltr"><br><div>I copied the draft note to a wiki page ... to facilitate the discussion
regarding per key last update date meta data.</div><div><br></div><div><a href="https://wiki.openstreetmap.org/wiki/Rarely_verified_and_third-party_data_staleness_in_OpenStreetMap">https://wiki.openstreetmap.org/wiki/Rarely_verified_and_third-party_data_staleness_in_OpenStreetMap</a> <br></div><div><br></div><div>Best regards,</div><div><br></div><div>Stuart </div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, 6 Apr 2020 at 11:56, European Water Project <<a href="mailto:europeanwaterproject@gmail.com">europeanwaterproject@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Dear Martin,<br><div><br></div><div>A date uses 3-4 bytes of memory. Just for brainstorming purposes, what would be the total database size inflation if all keys on all nodes, ways and relations in OpenStreetMap had 4 extra bytes of date meta data ?</div><div><br></div><div>Best regards,</div><div><br></div><div>Stuart</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, 6 Apr 2020 at 11:42, Martin Koppenhoefer <<a href="mailto:dieterdreist@gmail.com" target="_blank">dieterdreist@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Am Mo., 6. Apr. 2020 um 10:13 Uhr schrieb Frederik Ramm <<a href="mailto:frederik@remote.org" target="_blank">frederik@remote.org</a>>:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
Secondly, this is a problem shared by all the "last survey" approaches:<br>
You're standing the logic on its head. You're essentially saying: "If<br>
the object has NOT changed in reality, please DO change it in OSM" (by<br>
updating the last-checked tag). This means that we're being asked to<br>
switch from mapping changes to mapping non-changes, with a potentially<br>
huge data inflation in OSM (in theory I could update the "last survey"<br>
of my local supermarket every time I shop there...). Your idea to<br>
identify potentially fast-changing things and concentrate on these<br>
softens the impact but still, we'd be churning out new versions of<br>
objects like crazy just to confirm they are still there. (Everytime you<br>
make a little change to one of the object's 10 tags, a full copy of the<br>
object is created in OSM.)<br></blockquote><div><br></div><div><br></div><div>I agree that the last survey date approach where "ordinary" tags are set, are crazy. On the other hand, it seems to be a topic that a significant number of contributors are interested in (currently ~710.000 tags for this). To do it better, maybe it could be stored in parallel? There is this long wish list for API 0.7 in the wiki ;-) <a href="https://wiki.openstreetmap.org/wiki/API_v0.7" target="_blank">https://wiki.openstreetmap.org/wiki/API_v0.7</a></div><div>Likely it would not be something to be implemented in the next 10 years or so, but at least it could be kept track of the idea and people could be pointed to it...<br></div><div><br></div><div>There could be another table which stores for every tag on every object a confirmation date (by explicit request, i.e. it would only be set when a contributor explicitly sets it on a tag on an object, and when objects are split these would have to be split as well). This would imply that no new object version is created for simple property confirmations that do not alter the object. <br></div><div><br></div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
Thirdly, also shared by many "last survey" approaches: If you tag a<br>
restaurant with a last survey date then exactly what have you surveyed?<br>
Just that it is still there? That is still has these opening hours? Or<br>
that it still gives you free water? There's potential from confusion here.</blockquote><div><br></div><div><br></div><div>yes, the last survey confirmations would have to be stored on tag level, not on object level. <br></div></div><div><br></div><div>Cheers</div><div>Martin<br></div></div>
_______________________________________________<br>
Tagging mailing list<br>
<a href="mailto:Tagging@openstreetmap.org" target="_blank">Tagging@openstreetmap.org</a><br>
<a href="https://lists.openstreetmap.org/listinfo/tagging" rel="noreferrer" target="_blank">https://lists.openstreetmap.org/listinfo/tagging</a><br>
</blockquote></div>
</blockquote></div>