1. A data processing system for composing queries, comprising: a data repository containing physical data structures containing data; an abstract model comprising logical field definitions mapped to the physical data structures in the data repository; a plurality of pre-defined abstract queries defined according to the abstract model and configured to retrieve the data from the data repository by referencing the abstract model; and a plurality of display profiles comprising a plurality of abstract query conditions defined according to the abstract model; a query processor configured to (i) convert one or more selected pre-defined abstract queries into one or more executable queries of a given query language by referencing the abstract model, (ii) convert one or more selected display profiles into transformed instances of the one or more selected display profiles by referencing the abstract model, wherein the transformed instances of the one or more selected display profiles are in the given query language, and then (iii) combine the one or executable queries and the transformed instances of the one or more selected display profiles to produce a merged executable query, while preserving the syntax of the one or more selected pre-defined abstract queries in the merged executable query.