[josm-dev] JOSM file format extensions

[Sebastian Klein]

Hi,

there are 2 tickets that require an extension of the josm file format. 
The first (#4043 - "Have an 'upload prohibited' flag in .osm files") 
should be easy, something like that:

<osm version='0.6' generator='JOSM' uploadintended='no'>
...
</osm>

And simply drop that additional attribute if the layer was not 
explicitly locked by the user.

Second one is #3804 - "Upload does upload unchanged 
nodes/ways/relations".  If you add a tag to some object and remove it 
later, that object is still modified. This leads to duplicate entries in 
the history when it is uploaded.

To prevent this, we either need to store the original object data (it is 
in the undo buffer anyway, so no memory problem) or generate a hash.

The first way there would be two versions of the same object in the 
saved file:

<osm version='0.6' generator='JOSM'>
  <node id='2546783' version='4' ... >
   <tag k='source' v='...' />
  </node>
  <node id='2546783' action='modify' version='-1' ... >
   <tag k='source' v='...' />
   <tag k='name' v='...' />
  </node>
</osm>

For the second alternative there would be just another attribute:

<osm version='0.6' generator='JOSM'>
  <node id='2546783' action='modify' originalcrc32='24a81d832' 
version='4' ... >
   <tag k='source' v='...' />
   <tag k='name' v='...' />
  </node>
</osm>

In the unlikely case of a check sum collision, it wouldn't cause much 
harm. (It would work the same way it does now. :)  )

What do you think? Feel free to suggest a better wording for the tags!

__

Sebastian