1. A method for integrating relational and hierarchical data, schema definitions, and queries in a data processing system, comprising the steps of: converting one or more schema definitions into an intermediate schema language component of an intermediate data language when one or more schema definitions are provided; converting one or more query expressions into an intermediate query language component of the intermediate data language when one or more query expressions are provided; and compiling, in an intermediate data language processing engine, at least one of the intermediate schema language component and the intermediate query language component into a run-time representation in accordance with a relational-hierarchical analysis; wherein the data processing system comprises a processor and memory for performing the converting and compiling steps.