I had two thoughts: a) Changing 'schemas' is supported by document, or advanced key-value, stores like Couch or Cassandra. You end up thinking of your objects

I had two thoughts: a) Changing 'schemas' is supported by document, or advanced key-value, stores like Couch or Cassandra. You end up thinking of your objects more as hashes and program accordingly; everything else is just a mapreduce task (ie, you've updated your schema. If you coded well, nothing should break because of that, but you'd like to update all of the old objects. So write a mapreduce task, like a migration, that does that). b) DataMapper, for ruby, is used mostly as an ORM; however, the "R" is pretty optional, as people have written data adapters for other architectures -- from CouchDB to the SalesForce API. Those are just some associated thoughts. I'm playing around with Cassandra and Couch on my server at the moment (grr, when I have a moment).