The present invention relates generally to data retrieval, and more particularly but not exclusively to obtaining referentially converted user data having user-defined data types. In one implementation, the present invention is a method for retrieving user data in a data system using one or more application programs for defining a layout for each user data type, defining one or more conversion routines for non-standard data types, calling a coordination call to map standard and non-standard data types, and retrieve the user data from the data storage device.