> I'm just now learning scheme and it seems to me that with its clean
> mathematical underpinning (overarching mathematical orientation?) it
> would make an ideal language for truly relational database
> Never having designed a language I would have NO IDEA what such a
> query language would look like.
A look into the logic programming camp may be worthwhile, at least if
you are interested into extensions of the classical relational model, too.
A random link, just googled:
Constraint Programming and Database Query Languages
As far as I --accidentally-- know, there is some research going on
about the expressiveness of database query languages. (Think of a
database relating railway stations: x is railwise next to y, and query
it for a connection from Irkutsk to Perpignan, in SQL -- or relational
algebra, for that matter...)