The following is from WikiWikiWeb:

A RelationalDatabase as implemented today (with tables, rows, SQL as query language) is much more complicated and less powerful than what a database should be in the RelationalModel. Tables and rows aren’t equivalent to relations and tuples, because SQL doesn’t support user-defined data types and because tables are bags, not sets. What is good enough varies with the complexity of the problem you are facing, and for some problems, the implementation of the relational model by current SQL DBMSes becomes really annoying.

SQL, like Java, C#, and many other languages, are statically typed. If I read the above quote correctly, the true theoretical “relational model” is really just a model of tuples: ~ a name ~ attributes ~ values for the attributes To me, that is the perfect definition of Ruby classes. By logical extension, the true relational model could therefore be implemented by a Ruby object database or datastore.