Coherent changes validation

The challenge is not just detecting that an object has changed, but understanding what that change actually means.

In OpenStreetMap, modifications are contributed in changesets that are not always coherent from a geographic, thematic, or temporal standpoint. These changes are then broadcast as Diff in chronological order, no longer grouped by OSM changeset. Moreover, a single object can be deleted, recreated, split, or merged in the same Diff or Changeset. It is necessary to reorganize this flow of changes in order to analyze it.

Clearance does not validate changes object by object, nor OSM changesets, nor in chronological order. It groups them into geographically coherent sets.

Geographic context of changes (LoCha)

Clearance introduces the concept of Logical Changeset (LoCha).

OSM modifications at the same location must all be accepted or all rejected at the same time, to guarantee a coherent state of the local copy.