1. A graphical user interface residing in memory, comprising: a) a query specification display area for specifying result fields and operators to define an abstract query, each result field corresponding to a logical field specification of a data abstraction model abstractly describing data in a database, the data abstraction model comprising metadata for mapping the result fields to the data in the database; b) a classification field specification display area for specifying classification fields for the abstract query, each classification field including a result field and an associated classification definition, the classification field specification display area comprising: a result field window displaying a plurality of available result fields; and a plurality of graphical elements configured to allow specification of classification definitions for one or more selected result fields from the plurality of available result fields, each classification definition being suitable for dividing data to be returned for a corresponding selected result field into a plurality of categories; and c) a first selection element for specifying whether the specified classification fields will be included with the abstract query for execution; and d) a second selection element for initiating execution of the abstract query according to the selection made using the first selection element.