1. A system for processing a query, the system comprising: a CPU, a computer readable memory, and a computer-readable tangible storage device; first program instructions to receive a first query expressed in a first query language other than XML database schema and relational database schema, the first query language including classes and properties; second program instructions, responsive to the receipt of the first query, to determine that an XML database includes a class and a property that correspond to a class and a property of the first query, translate the first query to an XML database schema of the XML database, and initiate search of the XML database for data responsive to the query translated to the XML database schema; and third program instructions, responsive to the receipt of the first query, to determine that a relational database includes a class and a property that correspond to the class and the property of the first query, translate the first query to a relational database schema of the relational database, and initiate search of the relational database for additional data responsive to the query translated to the relational database schema; and wherein the first, second and third program instructions are stored on the computer-readable tangible storage device for execution by the CPU via the computer readable memory.
1. A system for processing a query, the system comprising: a CPU, a computer readable memory, and a computer-readable tangible storage device; first program instructions to receive a first query expressed in a first query language other than XML database schema and relational database schema, the first query language including classes and properties; second program instructions, responsive to the receipt of the first query, to determine that an XML database includes a class and a property that correspond to a class and a property of the first query, translate the first query to an XML database schema of the XML database, and initiate search of the XML database for data responsive to the query translated to the XML database schema; and third program instructions, responsive to the receipt of the first query, to determine that a relational database includes a class and a property that correspond to the class and the property of the first query, translate the first query to a relational database schema of the relational database, and initiate search of the relational database for additional data responsive to the query translated to the relational database schema; and wherein the first, second and third program instructions are stored on the computer-readable tangible storage device for execution by the CPU via the computer readable memory. 5. The system of claim 1 wherein: the class of the first query specifies a type of data; and the second program instructions determine that an XML database includes a class and a property that correspond to the class specified in the first query, and determine that a relational database includes a class and a property that correspond to the class specified in the first query, by reading a table which lists both the XML database and relational database as including sources of data for the class specified in the first query.