Berkeley DB XML
(XML.com via Dive Into Mark)
Berkeley DB XML is an open source, embedded XML database created by Sleepycat Software. It’s built on top of Berkeley DB, a “key-value” database which provides record storage and transaction management. Unlike relational databases, which store data in relational tables, Berkeley DB XML is designed to store arbitrary trees of XML data.
I’ll give a cookie to the first person who gets Cocoon working with this… :)