----- Original message -----
From: Steve Hanson/UK/IBM
To: DFDL-WG <dfdl-wg@ogf.org>
Cc: Alex Wood1/UK/IBM@IBMGB, Andrew Edwards/UK/IBM@IBMGB, Mark Frost/UK/IBM
Subject: Clarification for nil processing and zero length
Date: Fri, Mar 4, 2016 11:35 AM
 
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