The type of a DFDL format property can be any of 'String', 'Enum', 'Boolean', 'Integer', 'QName','Character', 'XPath 
Expression'

The 'String' type is not specific enough. Sometimes it describes a property which is a 'DFDL string literal' and can 
contain any of the mnemonics described in section 6.3.1. In other places, 'String' describes a property which clearly 
should not use generic mnemonics such as %WSP; but could be specified using non-generic mnemonics.

This has caused confusion in the implementation team because readers have assumed that 'String' means 'DFDL string 
literal' in all cases.