Axiom is an object database, it uses SQLite for its backend. Axiom is very young , still it supports a significant portion of the features present in the databases.
Axiom has grown out of Atop (Atomic Transactional Object Persistor), You can build object-oriented applications that take advantage of queries, its not just a wrapper (like SQLObject) placed around existing database, but it is a fully-featured object database. Axiom comes with an implementation of Twisted’s IRealm interface. This means an Axiom store can be given to a portal to allow authentication and authorization against it, using the standard Twisted Cred APIs.
Axiom is suitable for a large number of database-driven applications although it has its own set of limitations. It provides an efficient, non-SQL interface to an existing relational database, it encourages a style where many objects are loaded with a small, often fixed number of queries. Objects stored in an Axiom database can refer to any other object stored in the same database (like Python references) also can provide a schema definition which allows in-memory constraints to be enforced.
Axiom is far from complete, its just three months old. Axiom