hexBinary is an opaque type
13.1 Properties Common to All Simple Types:
Opaque: representation is assumed to be ‘binary’ and the representation property is not examined.

I created a test to verify that the representation property is not examined. This test originally passed, but now I get the following error:

[info] - test_hexBinary_rep *** FAILED ***
[info] java.lang.Exception: Schema Definition Error: Implicit Alignment is not allowed for HexBinary with representation='text'. Use representation='binary' instead.() Schema context: element.hB_rep. Location line 4391 column 107 in file:/home/jchab/NGF/dfdl/daffodil-test/target/scala-2.9.2/test-classes/edu/illinois/ncsa/daffodil/section05/simple_types/SimpleTypes.tdml.

If this is the intended behavior, then the spec is misleading.