You can query properties of related objects. Just make sure, that the properties will be generated in the query widget:
from tw.rum.querybuilder import query_fields @query_fields.around("issubclass(resource, Participation)") def _query_fields_participation(next_method,resource): return next_method(resource)+["person.lastname", "person.firstname"]
At the moment no deeper nestings are supported.
Multiple relation to the same resource should work fine, as we use aliasing internally.