Best approach when data store is XML instead of a database?

Hi all,

Does anyone know of an approach/plugin that for model classes persisted
to XML, as ActiveRecord works with databases? I'm aware of
ActiveRecord::XMLSerialization, but I'd like to expand on that in two

1) The 'to_xml' method currently serializes descendant objects only when
explicitly specified. I need to be able to say 'to_xml(:include =>
:all)', so a complete document is written.

2) I'd like the XML schema to drive the definition of the model classes
(like ActiveRecord). Doesn't matter to me if that happens at run time
or via a rake task.

We're trying to avoid the ORM quagmire. We have complete control over
both the XML schema and the model classes, so we can change the schema
if necessary.