[DFDL-WG] Clarification for nil processing and zero length

[Steve Hanson]

No, because for a complex element to be nil the only allowable value is 
empty string, so WSP* is too permissive.

Regards
 
Steve Hanson
IBM Integration Bus, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890



From:   Andrew Edwards/UK/IBM
To:     Steve Hanson/UK/IBM at IBMGB
Cc:     Alex Wood1/UK/IBM at IBMGB, Mark Frost/UK/IBM at IBMGB, dfdl-wg at ogf.org
Date:   04/03/2016 13:06
Subject:        Re: Clarification for nil processing and zero length



I agree with the proposed change.  Would it also apply to 9.3.2.2 for 
complex elements?  That has very similar words.
 
Cheers,
Andy Edwards
Software Engineer
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----- Original message -----
From: Steve Hanson/UK/IBM
To: DFDL-WG <dfdl-wg at ogf.org>
Cc: Alex Wood1/UK/IBM at IBMGB, Andrew Edwards/UK/IBM at 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 at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
 

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