Datamapper

A Data Mapper is a layer of software which abstracts the database away from the rest of the code and isolates the application logic from the database internals. This allows code to be written which accesses the data stored in the database without needing to deal with the database at all. They need no SQL interface code and no knowledge of the database schema; in fact there needn't be a database at all. Different datamappers can be written which produce random data for testing or retrieve data via XMLRPC from a remote server, to name a few examples.