a downstream record thus the field may contain a pointer to a downstream record in the form of a sub list name alternatively in an object oriented environment the connection to the downstream record may involve object messaging if decision step 88 determines that the downstream field contains a sub list name or otherwise identifies a downstream record then the sh list resolution routine explained with reference to fig2 is called and executed for that downstream record identified by the sub list name or pointer or object messaging in the field under consideration it is important to note that the process described with reference to fig2 and 23 is highly recursive referring back to fig2 the process record fields routine step 72 occurs midway through the sh list resolution routine then in the course of the execution of the process record fields routine as shown in fig2 the sh list resolution routine step 90 may be called and executed to process the field under consideration the result of this recursiveness and the nesting of process records fields routines within sh list resolution routines and vice versa is that for each record and for each field of that record the schema branches are followed downwardly left to right until the bottom most branches of the schema tree are reached during this process oid and ludt information is percolated back upward through the schema tree checksums at differencing levels are computed based on this percolated information returning to decision step 88 if the determination is made that the field does not contain a sub list name or pointer or involve object messaging then in add variable step 92 the variable identified by the field is added to a variable pool for the field in step 94 the routine of fig2.