An integration server system for mapping data objects on a database schema
offers a strongly-typed model API, complex constraint management, and
association balancing. The integration server system also has improved
performance through optimized handling of ordered associations of data
object and of string-valued attributes. The integration server system
comprises a database schema configured to store a set of data object
instances. A metadata model represents a configuration of the set of data
object instances in the database schema. A model application programming
interface provides a client application with access to the set of data
object instances, and a metadata application programming interface
provides a client application with access to the set of data object
instances via the metadata model.