In simple cases, a manipulator produces correct output and can be annotated with "supportsIncrementals=true" if it meets all of the following criteria:

If the answer is yes to these four questions, then a manipulator can be annotated with "supportsIncrementals=true". If the answer is no to any one of these questions, then further analysis is required to determine whether correct output can be produced, and further work is required to produce correct output. This work typically involves maintaining state.

If the answer is yes to all but the second question, it may be possible to support incremental input with only a little extra work to address the records that the manipulator does not output. To be correct, a manipulator should emit a delete record for any record that it had previously output but is now not being output. (Recall that a record marked for deletion has an Endeca.Action property set to DELETE.)

This would require the manipulator to track what records it had previously output. To make such implementation easier, a manipulator can replace input records that it should not output with a delete record instead.

For example, suppose a manipulator filters records to include only those records that contain a color property that is set to red. Record A has the property color set to red, so the manipulator includes record A. In a subsequent incremental acquisition, record A has changed so that now the color property is set to blue. Record A no longer meets the manipulator's filtering criteria. Instead of dropping the record, the manipulator emits a delete record for record A.