8. A non-transitory computer-readable medium containing a program which, when executed by a processor, performs an operation of modifying data stored in a database, the operation comprising: retrieving a modification operation specification specifying at least one logical field used as part of one of physical entity identification criteria or selection criteria in performing the abstract modification operation, wherein the modification operation is a delete operation and wherein generating the abstract query, comprises: specifying a logical seed field to delete, creating an abstract delete expression using the specified logical seed field, specifying a selection condition for selecting data to delete, and adding the selection condition to the abstract delete expression; generating an abstract query specifying the modification operation to modify data in the database, wherein the abstract query comprises a plurality of logical field names and corresponding values, wherein the plurality of logical field names are items of definitions of logical fields defined in a logical data model, and wherein each of the logical field definitions further include at least one location attribute identifying a location of physical data corresponding to the logical field name of the respective logical field definition, and a reference to an access method selected from at least two different access method types, and wherein the access methods map the respective logical fields to physical entities of the database; transforming the abstract query an executable query consistent with the particular physical data representation according to the access method specified by each logical field included in the abstract query; and executing the executable query, whereby data in the database corresponding to the logical fields is modified.
8. A non-transitory computer-readable medium containing a program which, when executed by a processor, performs an operation of modifying data stored in a database, the operation comprising: retrieving a modification operation specification specifying at least one logical field used as part of one of physical entity identification criteria or selection criteria in performing the abstract modification operation, wherein the modification operation is a delete operation and wherein generating the abstract query, comprises: specifying a logical seed field to delete, creating an abstract delete expression using the specified logical seed field, specifying a selection condition for selecting data to delete, and adding the selection condition to the abstract delete expression; generating an abstract query specifying the modification operation to modify data in the database, wherein the abstract query comprises a plurality of logical field names and corresponding values, wherein the plurality of logical field names are items of definitions of logical fields defined in a logical data model, and wherein each of the logical field definitions further include at least one location attribute identifying a location of physical data corresponding to the logical field name of the respective logical field definition, and a reference to an access method selected from at least two different access method types, and wherein the access methods map the respective logical fields to physical entities of the database; transforming the abstract query an executable query consistent with the particular physical data representation according to the access method specified by each logical field included in the abstract query; and executing the executable query, whereby data in the database corresponding to the logical fields is modified. 9. The computer-readable medium of claim 8 , wherein transforming the abstract query comprises determining a corresponding physical location of data for the specified logical seed field.