1. A method, in a data processing system, comprising: obtaining entity metadata constructs for an object relational mapping framework, the entity metadata constructs mapping fields in entities of an object model to fields in a data table of the nested relational database and identifying relationships between entities in the object model; obtaining a nested relational data model of the nested relational database, the nested relational data model specifying tables and sub-tables of the nested relational database; mapping tables and sub-tables of the nested relational database to a plurality of separate entities of the object model, wherein at least one parent table is mapped to at least one top-level entity and at least one sub-table is mapped to at least one sub-entity of the at least one top-level entity; and accessing data in the nested relational database using the plurality of separate entities, wherein: the mapping is performed without normalizing the data of the tables and sub-tables of the nested relational database to a non-nested representation, mapping tables and sub-tables of the nested relational database to a plurality of separate entities of the object model comprises providing a nested relational entity provider and using the nested relational entity provider to perform the mapping, the nested relational entity provider loads a top level entity and at least one sub-entity of the top level entity using a single read operation on a record of the nested relational database, and the record includes at least one multi-value field identifying at least one sub-entity.