The keys are used, they are the index of the column, used to identify the column name from the transformedColumns, eventually.  If we had just the value, we'd lose out on which column that value came from....   Make sense, or did I miss something?   Were you referring to the line this.delegateIterator = this.backingData.dataContainer.entrySet().iterator() ?  [which we are iterating over at line 54 above].