Calling setVariable more than once results in a Parse Error but the spec states that this should be a Schema Definition Error.

"Even if the errors are detected at processing time, the errors associated with write-after-read, and double-write are schema definition errors because they indicate the schema is not properly designed to use variables consistent with their single-assignment behavior."

See test doubleSetErr in daffodil-test/src/test/scala/edu/illinois/ncsa/daffodil/section07/variables/TestVariables.scala for the current behavior.