Understanding Object-Relational Mappings

Relational mappings define how persistent objects reference other persistent objects. Oracle Application Server TopLink supports the following object relational mapping types:

Array mappings are similar to direct collection mappings, but map to object-relational array data-types (the Array type in JDBC 2.0 and the VARRAY type in Oracle8i). Use array mappings to map a collection of primitive data. See "Working with Array Mappings" for more information.
Object array mappings are similar to array mappings, but map to object-relational array data types. See "Working with Object Array Mappings" for more information.
Structure mappings are similar to aggregate object mappings, but map to object-relational aggregate structures (the Struct type in JDBC 2.0 and the OBJECT TYPE in Oracle8i). See "Working with Structure Mappings" for more information.
Reference mappings are similar to one-to-one mappings, but map to object-relational references (the Ref type in JDBC 2.0 and the REF type in Oracle8i). See "Working with Reference Mappings" for more information.
Nested table mappings are similar to many-to-many mappings, but map to object-relational nested tables (the NESTED TABLE type in Oracle8i). See "Working with Nested Table Mappings" for more information.

These mappings allow for an object model to be persisted into an object-relational data-model. Currently, the TopLink Mapping editor does not support object-relational mappings-they must be defined in code or through amendment methods. See "Working with Object-relational Descriptors" for more information.