11. The computer program product of claim 9 , wherein the computer readable program when executed on a computer further causes the computer to: request the database of each relational database entity to check for authorization for each of its associated predicates; receive the authorization rule including an authorization filter for each predicate from its associated database of the relational database entity, wherein the authorization filter specifies unauthorized data; and apply the received authorization filters to the received query result to remove unauthorized data prior to providing the query result set to the user.
9. A computer program product comprising a computer useable memory device having a computer readable program stored thereon, wherein the computer readable program when executed on a computer causes the computer to: provide a pre-defined logical schema to a user of a database system, wherein the pre-defined logical schema is mapped to at least two relational database entities of different databases storing data therein; receive a logical query for data stored in the databases from the user, wherein the logical query is written in an object-oriented query language utilizing the pre-defined logical schema, and comprises two or more predicates and an operator specifying an action to take with one or more of the predicates; in response to receiving the logical query, interpret the logical query using the pre-defined logical schema to determine which of the relational database entities is a subject of the logical query, and which of the relational database entities is associated with each predicate; request the database of each determined relational database entity of the logical query to: translate each of the associated predicates of that database in the logical query into a query language specific to that database, wherein at least two different databases translate an associated predicate; and apply an authorization rule with each of the associated predicates of that database in the logical query, wherein the authorization rule identifies unauthorized data; receive a translated predicate query for each determined predicate of the logical query from its associated database of the relational database entity, wherein each translated predicate query is written in a relational query language specific to the associated database and is a translation of one of the object-oriented predicates in the logical query; combine each translated predicate query received from the databases of the determined relational database entities into a master query using the operator; execute the master query against the databases of the relational database entities that are subjects of the logical query; in response to executing the master query, receive a query result set from the databases of the relational database entities that are subjects of the logical query; and provide the query result set to the user, wherein the query result set lacks the unauthorized data.