I created a test where the fn:empty function references an element that does not exist. In this case I would expect a Schema Definition Error. However, the parse does not fail, and fn:empty is set to true.

This will potentially be fixed as part of the DPath changes, but currently, when run against the DPath branch, this test fails because fn:empty has not yet been implemented.

See test empty_09 in the following files:
scala-debug/edu/illinois/ncsa/daffodil/section23/dfdl_expressions/TestDFDLExpressionsDebug.scala
scala/edu/illinois/ncsa/daffodil/section23/dfdl_expressions/TestDFDLExpressions.scala
daffodil-test/src/test/resources/edu/illinois/ncsa/daffodil/section23/dfdl_functions/Functions.tdml