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

[Steve Hanson]

Issue raised: https://redmine.ogf.org/issues/309

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:   Mike Beckerle <mbeckerle.dfdl at gmail.com>
To:     Steve Hanson/UK/IBM at IBMGB
Cc:     DFDL-WG <dfdl-wg at ogf.org>
Date:   04/03/2016 14:59
Subject:        Re: [DFDL-WG] Clarification for nil processing and zero 
length



My read of 13.16 says that for nilKind 'literalValue' and textual 
representation, WSP* is already allowed for simple types.  So I think 
nilValue="%WSP*;" should work and match empty string.

Delimiters have qualifiers on ES alone and WSP* alone e.g., for separator: 
"However, the WSP* entity cannot appear on its own as one of the string 
literals in the list when determining the length of a component by 
scanning for delimiters, , and it is a schema definition error otherwise. 
delimiters"

(Note the fragment at the end of that sentence. That's a spec. bug)

But I see no such stipulation for nilValue. 


Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | 
www.tresys.com
Please note: Contributions to the DFDL Workgroup's email discussions are 
subject to the OGF Intellectual Property Policy


On Fri, Mar 4, 2016 at 6:35 AM, Steve Hanson <smh at uk.ibm.com> wrote:
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
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

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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
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