OS X Spotlight searching from a user-defined database?

Since 10.5, Spotlight on Mac OS X has this nice Dictionary integration you might have seen:

Any ideas how anything like this could be implemented?

It seems that the current Dictionary+Spotlight friendship is somewhat hardcoded into Spotlight's code (for example, there is a specific user defaults key com.apple.spotlight.DictionaryLookupEnabled present just for toggling dictionary searching).

I've read in the Spotlight Importer Programming Guide that one can create a Spotlight importer only on a per-document basis开发者_运维问答, that is if your application Foobar opens/creates files with extension .foo, you can then write a Spotlight importer for indexing properties of those files.

What I need, however, is for the Spotlight to somehow query some sort of a database with its own query (exactly what it now does with Dictionary).

That's not possible, sorry; you need to create a file per Spotlight match. File an enhancement request.