The TDML page https://daffodil.apache.org/tdml/
"threePass - - parse given data, compare to expected infoset expect failure. If failed, unparse infoset to first output data, compare to given data, expect failure. If failed, parse first output data to second infoset. Compare to expected infoset, expect failure. If failed, unparse second infoset to second output data, compare to first output data, expect success. For unparsing, the values can be"
See the fragment of a sentence at the end? That's not supposed to be part of this paragraph. It is the introduction for the next block of definition items.