Am 28.11.18 um 10:15 schrieb James Heald:
It should also be made possible for the local wikibase to use local prefixes other than 'P' and 'Q' for its own local properties and items, otherwise it makes things needlessly confusing -- but currently I think this is not possible.
I think the opposite is the case: ending up with a zoo of prefixes, with items being called A73834 and F0924095 and Q98985 and W094509, would be very confusing. The current approach is to to use the same approach that RDF and XML use: add a kind of namespace identifier in front of "foreign" identifiers. So you would have Q437643 for "local" items, xy:Q8743 for items from xy, foo:Q873287 for items from foo, etc. This is how foreign IDs are currently implemented in Wikibase.