AIV GRB building import
We're importing buildings in Flanders (Belgium) from a database called GRB, published by government agency AIV.
You can safely ignore them! Do not let it stop you from correcting things. The source:geometry:ref tag refers to the object number in the source data. In the workflow, this tag is used to make it easy to check if all the buildings in GRB are also in OSM already. If you delete the tag, the next one around who wants to import in the area will think it might have to be added. But they will look at your work and keep the best elements of both datasets. The source:geometry:date tag refers to the moment the object was updated in GRB. This can help you to see if the GRB is maybe outdated now. When an object is updated in GRB, this tag will change. The tool will then say "oh, but you should import the geometry of this object again".
The tools are available for everyone, with specific guidelines in order to achieve optimal quality. We are not dumping data in OSM but look at the data critically and compare with different sources to ascertain that it makes sense (the government address database CRAB, aerial imagery, street-level imagery, surveys...)