The DFDL 1.0 spec current says: 9.3.2.1 Simple element If the result is length zero as described above, the representation is then established by checking, in order for: 1. nil representation (if %ES; is a literal nil value). 2. empty representation. 3. normal representation (xs:string or xs:hexBinary only) 4. absent representation (if none of the prior representations apply). But should bullet 1 be: 1. nil representation (if either %ES; or %WSP*; on its own is a literal nil value). I added a test to IBM DFDL and found that setting dfdl:nilKind="literalValue" & dfdl:nilValue="%WSP*;" did not match an element value of empty string. That surprised me, and I think the IBM DFDL code is strictly implementing bullet 1. Using "%WSP*;" is useful for allowing zero or more white space to mean <nil>. I could use "%WSP+; %ES" to achieve the same goal but I'm not sure that was the intent here. Quick response appreciated. Regards Steve Hanson IBM Integration Bus, Hursley, UK Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh@uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890 Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU