IBM has been creating public DFDL schemas for various data types. When these are released, we try to parse data against the schema using Daffodil for compatibility's sake. A set of DFDL schemas that model HL7 v2.7 messages are now available in a DFDLSchemas GitHub repsitory at http://dfdlschemas.github.io/HL7-v2.7/
(View on github)