CrossingChasms is a large pattern language that describes how to connect an object system to a RelationalDatabase.
If you'd like the complete text of the language, send email to mailto:kyle.brown@acm.org or visit our web site at http://members.aol.com/kgb1001001/Chasms.htm (a BrokenLink) [still exists on the InternetArchive: http://web.archive.org/web/20030402004741/http://members.aol.com/kgb1001001/Chasms.htm]. A few patterns from the extended language that are available on wiki are:
-- KyleBrown
You might also want to read TheThirdManifesto, which addresses the object-relational divide from another direction.
See CrossingTheChasm (a book by GeoffreyMoore)