Currently, only $datastore is accessible to Attribute Rule immediate calculation, which means the spatial operation, e.g. intersect, can't be performed on the feature layer in another database.
In our case, we have editing database and browse database. The browse database provides reference data to the editing process. We need to do spatial query to the layers from the browse database. Since the current global variables do not allow to access layers from other database, we have to write code using C# and SDK, which needs a programmer to do the job.
The best solution should be that we can use the layers in a map to do spatial operation in attribute rule.
Thanks...