The main components of each ODI mapping are the datastores. ODI Generator creates ODI datastores based on schema information (structured data  describing file/tables and their attributes) present on its repository. Schema information consists in standard technical information which can be extended adding information which is specific to your data integration project.
Code Generator component reads this information using a dedicated API and generates CREATE DATASTORE statements which are subsequently transformed in Oracle Data Integrator datastores by the ODI Engine component.

Information about files/tables and attributes can also be used to create simple Oracle Data Integrator mappings.
This is possible when the business rules used in mapping can be extrapolated from the definition of one datastore: for example when loading a file in a landing table taking as granted that the landing table has the same structure as the source file and the attribute names and data types can be derived from file's attributes.