33. A method of enabling a client application executing on a computer to perform operations on data objects defined by a model description stored in a machine-readable medium along with a database schema including one or more database tables configured to store a set of data object instances in a database created from the model description and a model application programming interface from the model description that enables the client application to access data objects in the set of data object instances in the same manner as other data objects, the method comprising: using the model application programming interface to create instance of data objects in the database schema including an instance of an object structure having one-to-one and one-to-many mappings; storing the created data object instances in a machine-readable medium; accessing the created data object instances as a separate data objects with the client application; and performing operations on the accessed data object instances including storing, reading and modifying attributes of the data objects.
33. A method of enabling a client application executing on a computer to perform operations on data objects defined by a model description stored in a machine-readable medium along with a database schema including one or more database tables configured to store a set of data object instances in a database created from the model description and a model application programming interface from the model description that enables the client application to access data objects in the set of data object instances in the same manner as other data objects, the method comprising: using the model application programming interface to create instance of data objects in the database schema including an instance of an object structure having one-to-one and one-to-many mappings; storing the created data object instances in a machine-readable medium; accessing the created data object instances as a separate data objects with the client application; and performing operations on the accessed data object instances including storing, reading and modifying attributes of the data objects. 41. The method of claim 33 further comprising ordering retrieved data by a value of an attribute of the data.