[OSM-dev] Unusual large Changesets - Could OSM server API split uploaded data in more then one changeset?

[Peter Wendorff]

Am 09.02.2014 15:33, schrieb Pierre Béland:
> Hi Peter,
> 
> Then  a warning could be given in editors such as JOSM highlighting such edits that cover large zones.
Yes, that would be useful. Nevertheless it's nothing in the API, but in
the Editors.

regards
Peter
> 
> 
>  
> Pierre 
> 
> 
> 
> ________________________________
>  De : Peter Wendorff <wendorff at uni-paderborn.de>
> À : dev at openstreetmap.org 
> Envoyé le : Dimanche 9 février 2014 4h59
> Objet : Re: [OSM-dev] Unusual large Changesets - Could OSM server API split uploaded data in more then one changeset?
>  
> 
> Hi Pierre,
> as far as I know: no, that's not possible.
> A changeset is not an atomic thing in OSM. It consists of a number of
> tags (most often source and changeset if any) and a number of osm object
> versions (nodes, ways and relations) and a bounding box.
> This bounding box afaik is a boundingbox containing all objects edited,
> but may be even larger.
> 
> Your propose the API to split this, but let's examine the following
> counter example:
> 
> You are really editing a large area, let's say, you check a big part of
> the coastline of a continent, let's say Europe.
> You loaded the coastline into the editor and then start working on
> fixing several gaps and bugs in it, going through a list of errors
> returned e.g. by some coastline-checker tool.
> 
> Let's say this list is not ordered along the coastline. Instead you fix
> the first error at the north sea coast of Latvia, then another one in
> Greece.
> After these two you decide to upload the first chunk of your changeset,
> but not to close it (which is possible!).
> 
> The changes are online and valid immediately, and therefore they have to
> have a changeset id they belong to. Thus at this point in time the API
> has to decide to split these two edits to two changesets or not.
> According to anything known up to know the changeset would be splitted,
> but in the following hours you fix hundrets of other errors in the
> coastline, and in the end every few kilometers there's an edit.
> Would you have done it in a different order, the API wouldn't have split
> the changeset at all, but now it's too late, many data consumers already
> have pulled the first edits of your changeset, stored them under the
> changeset ID the API decided at first.
> 
> Nevertheless I think you write about something which would indeed be
> very useful, and that is to split the visual bounding boxes of one
> changeset into several parts.
> 
> Currently each changeset is visualized as one big bounding box, but
> instead it would in fact be much more useful to e.g. visualize it as all
> affected tiles. Your changeset would then appear as two blobs of color,
> one small box in Mali and another one in Bolivia.
> 
> But that's not a problem of the API and of the Changeset Bounding box,
> but of the Visualization of Changesets and the algorithm pascal uses to
> calculate the activity area.
> It's the only simple way to get the activity area, as the bounding box
> is the only coordinate to get by changeset without inspecting every
> element inside, so it's a perfectly valid way to go, and it works most
> often.
> Inspecting further would require the API or the consuming application
> (eg. wdyc and Pascals contributor statistics) to do much more work, and
> it's the question if that's worth it.
> 
> regards
> Peter
> 
> 
> Am 08.02.2014 20:17, schrieb Pierre Béland:
>> See changeset where editing only in bottom left corner and upper
>> right corner http://www.openstreetmap.org/changeset/20447101
>>
>> The bbox of the changeset above is not very instructive of the zone
>> covered by this edit.  I updated one way in Mali. Then forgot to save
>> before I moved to Bolivia for other editing again in a small area.
>>
>> For example, if I look at contributor statistics for Bolivia with 
>> Pascal Neis new Contributor statistics by a specific comment, I see a
>>   small box for Bolivia, and a large box covering two continents,
>> simply due to this single changeset. 
>> http://resultmaps.neis-one.org/osm-changesets?comment=hotosm-bolivia
>>
>> Such large bbox create problems when we want to analyse Contributor
>> activities in one area extracting Changesets for a particular bbox.
>> It is also difficult to assure follow-up of activities in a local
>> zone you take care of.
>>
>> To correct this problem, could the OSM API that take care to upload
>> data to the OSM database analyze such Changesets that cover a large
>> zone, in particular more then one continent, and split them if
>> necessary in more then one changeset?
>>
>>
>>
>>
>>
>> Pierre
>>
>>
>>
>> _______________________________________________ dev mailing list 
>> dev at openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
>>
> 
> 
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