1. A method for processing a data access request, comprising: receiving a user request to perform a model entity operation that includes an indication of at least one instance of a model entity and a desired query operation, wherein the model entity is defined by a database abstraction model logically describing an underlying database and wherein the model entity defines the focus for a query operation, and wherein instances of the model entity are distinguished by an identifier in an underlying database; retrieving, in response to the request, a linking function configured to identify instances of the model entity that are related to the at least one instance of the model entity, according to a predefined relationship; and performing the model entity operation by: invoking the linking function to retrieve any related instances of the at least one instance of the model entity; executing the desired query operation against any retrieved instances of the model entity, and; returning instances of the model entity identified using the linking function that satisfy any conditions specified by the query operation.