While it has relevance for these OKVS based SRFIs, for conventional SQL RDBMSes I was thinking they're such a can of worms that after these SRFIs get sufficiently perfected, a mailing list and defacto working group like the ones for Schemedoc and Schemeweb might be created.
Hopefully by that time I'll have a SRFI text if not yet an implementation. Note that RelationsCowan does *not* support the conventional SQL model, but Codd's original relational model as developed by Date and Darwen and adapted to a dynamically typed language. In particular, attributes (columns) and tuples (rows) are *sets*. Attributes (columns) have no ordering, tuples (rows) have no ordering, and both attributes and tuples must be unique in a given relation.
No disrespect for the SRFI-168 N Tuple database model intended, but just as some data are unnatural for RDBMSes, some are very natural, and RDBMSes bring a lot of messy power to the table, as we've been discussing WRT to validation.
My idea here was to put the RDBMS on top of the n-tuple database, keeping each table in a different prefix (which means a separate nstore object). Conversely, it is also possible to expose a SQL database as a set of nstores, where the prefix argument is the table name.