An object label uniquely identifies objects in the same class that are tested against each other in clauses and subclauses of a rule.
For example:
Check for fire_station objects A that there are at least 5 fire_station objects B for which fire_station:B.geometry is within 10000m of fire_station:A.geometry
The object labels A and B distinguish between the root object and objects found in the subclause, both of which have the same class label fire_station and come from the same class.
For example:
Check for excl_zone objects that there are no objects X for which
X.geometry intersects excl_zone.geometry
In this example, the subclause is executed over all objects except exclusion zones. In this rule, the top-level object has a class label of excl_zone and no object label. The object in the subclause has no class label and an object label of X.
The following example shows how class and object labels are used independently:
