Class models in the cloud platform framework and the ones you develop yourself are transparently persisted using state of the art persistence technology.
The complete, object oriented paradigm with inheritance and associations is available to you without restrictions. You don't even have to add any methods or attributes explicitly to your classes to support their persistence.
Even with this high level of automatic, transparent persistence there may be sometime when you want to control how certain classes, attributes or relationships are persisted. With the pagebloom cloud platform you have that level of control if required - right down to the naming of table names, columns, indexes etc.,