I think I have mentioned before that the Telenav OSM team is always thinking of more ways to help improve OpenStreetMap. Something we have recently started looking into is supplying proposed changes directly as JOSM compatible XML files. This way, we could propose changes and additions to the map in chunks, instead of one by one like we have done for MapRoulette thus far.
So looking into the JOSM file format, we created a small (hypothetical) test file that just adds some ways that connect to the current network. Shown below is the process of merging that test file with existing OSM data in three stages: Base OSM layer, change layer overlaid, and finally the merged result.
Did you just notice something STRANGE here? When I made the change layer visible, some but not all the new ways appeared on the map - but after merging, the ways all appear. What makes this even weirder is that I can select the invisible way in the change layer, see and change tags etc. Is this a JOSM bug or is there something about the JOSM file format I do not understand?
If you want to try it for yourself, here is a zip file with both the base OSM data and the proposed change file.