[OSM-dev] Representing differences between sets of OSM data

[Immanuel Scholz]

> In JOSM you get data which is unmodified too. Also the data in JOSM is
> complete, i.e. if there is a way, then you also have the relevant
> segments and nodes which it references.

Not necessarily. JOSM still supports incomplete ways and the fact the
current server implementation does not return them via map-request may
change in future (e.g. because of relationships or other server
implementations)


> In theory I could probably adapt the planetdiff format to be closer to
> that used by JOSM but I'd need to be convinced it was really worth the
> effort. I'd be against adding information about the unmodified nodes and
> segments to the diff since this would increase the file size and also
> break the streaming algorithm which the diff tool currently uses.

Just remove the unmodified stuff from the xml file. JOSM can parse any
subset of an osm-file back, however, some objects will be incomplete or
ignored at all (JOSM will not import incomplete segments for now).


Bear in mind, that the JOSM approach was taken so that "changesets" and
"normal" xml files are readable by the same parser.

Note also, that you can store any "historical" objects with the same id
into a XML file and JOSM will happily ignore all but the last tag (which
should be changed to "all but the one with the highest timestamps",
perhaps). This way you can store "original" values in changesets without
changing JOSM at all.


There are some other unofficial additions to the osm-schema made by
JOSM, e.g. the tag "bound".


Ciao, Imi.

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