Hi!
I somewhat didn't jump here, as we simply don't use interwiki table on WMF sites, so the topic was out of interest. :)
It seems to me that if we want to modify the core to support interwiki integration, there are any number of core tables that could benefit from DB name fields.
I personally don't like the "interwiki integration", as pretty much nearly everything has to go through one of these methods:
1. Pulling from all wikis 2. Pushing to all wikis 3. Having central backend
All these have their own nightmares, and separation was quite often preventing us from madness. CentralAuth has added its own share of inefficiencies that nobody has been working on yet. Having shared data between multiple systems isn't the easiest problem usually, and it needs more attention than a single-time feature deployment.
E.g., user_newtalk could have a DB name field, so that users could be informed which wiki(s) they have new messages on.
Nooooeeesss (you're suggesting 2 here... :)
in the harder cases it will make more sense to have global tables, kinda like what CentralAuth sets up, unless we want to do a major revamping of the code.
I have no idea what major revamping you have in mind, when it comes to data sharing.
Do note that we don't have any data consistency framework for cross-database publishing, so you will always end up with inconsistencies around, that are not guarded by transactions. For each feature that means building a conflict/consistency management.. :)
Domas