A query on one repository can consult another with a federated service clause, typically to filter content by space membership: fetch the members from spaces, then keep only the rows whose publisher is among them. Such a clause is best written as a self-contained sub-query sharing no variables with the rest, so it runs once rather than once per row.

In a query template the repository is named with the generic address https://w3id.org/np/l/nanopub-query-1.1/repo/…, which resolves to whichever instance answers, never with the name of one server.