I think you've just invented "views".
"The adjective "suitable" in the description of the database must, of course, include some pretty impressive and reliable security features that not only prevents abuse but also prevents one gov department from seeing data relevant only to a different department."
If you consolidated all the data into one giant table and hosted it on a mature relational database system such as DB2 - you could then create views for different departments - omitting or including columns depending on requirements. Bog standard and very secure part of any industry-strength DBMS.
Biting the hand that feeds IT
