[DFDL-WG] New Experimental Feature document: dfdl:emptyElementParsePolcy

Wed Nov 27 11:25:20 EST 2019

OK so that sounds fine. 

Similar concern for unparsing though. What happens today if I omit a 
required occurrence from the infoset, but there is a default value on the 
element declaration? Hopefully you give an error rather than just 
continuing.

Regards

Steve Hanson
IBM Hybrid Integration, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday 

From:   Mike Beckerle <mbeckerle.dfdl at gmail.com>
To:     Steve Hanson <smh at uk.ibm.com>
Cc:     DFDL-WG <dfdl-wg at ogf.org>
Date:   22/11/2019 19:43
Subject:        [EXTERNAL] Re: [DFDL-WG] New Experimental Feature 
document: dfdl:emptyElementParsePolcy

Actually daffodil doesn't insert defaults when parsing, it creates the 
element, having no value, and then on-demand, when accessed, the value is 
pulled from where we save it in the static runtime data structures, and is 
saved as the element's value.  This can happen when an expression refers 
to the element, or when the data set is subsequently output as some other 
representation like JSON or XML.

So we *are* somehow doing defaults when parsing. Just not at the time the 
parser traverses the element.  For all intents and purposes we are doing 
defaulting during parsing. Not unparsing yet though. 

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, Nov 22, 2019 at 11:57 AM Steve Hanson <smh at uk.ibm.com> wrote:
Mike 

The new document looks good, the descriptions of the property values are 
clear and simple. 

One comment of yours I need to follow up though. You said: 

" Bug in this doc. Daffodil is not inserting defaults here (doesn’t 
implement default insertion when parsing.)  Fixed with new language you 
suggested. " 

Are you saying that if Daffodil parses an occurrence and determines it has 
the empty rep, and there is a default value on the element declaration, 
that the default value is not used?  If so then what happens?  Further, if 
you subsequently change Daffodil so it does use the default value, you 
have silently changed parsing behaviour in an incompatible way. IBM DFDL 
similarly does not use default values when parsing, but to prevent a 
future incompatible behaviour change, if we find a zero-length occurrence 
and there is a default value, we throw a runtime SDE. 

Regards

Steve Hanson 
IBM Hybrid Integration, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday 

From:        Mike Beckerle <mbeckerle.dfdl at gmail.com> 
To:        Steve Hanson <smh at uk.ibm.com> 
Cc:        DFDL-WG <dfdl-wg at ogf.org> 
Date:        16/10/2019 19:19 
Subject:        [EXTERNAL] Re: [DFDL-WG] New Experimental Feature 
document: dfdl:emptyElementParsePolcy 

I have revised this per your comments, and uploaded a new revision. Link: 
https://redmine.ogf.org/dmsf_files/13596?download= 

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 Wed, Oct 16, 2019 at 12:23 PM Steve Hanson <smh at uk.ibm.com> wrote: 
Mike 

Some significant comments on this. 

Regards

Steve Hanson 
IBM Hybrid Integration, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday 

From:        Mike Beckerle <mbeckerle.dfdl at gmail.com> 
To:        DFDL-WG <dfdl-wg at ogf.org> 
Date:        14/10/2019 19:58 
Subject:        [EXTERNAL] [DFDL-WG] New Experimental Feature document:   
     dfdl:emptyElementParsePolcy 
Sent by:        "dfdl-wg" <dfdl-wg-bounces at ogf.org> 

Per one of our trackers I uploaded an "official" document to describe this 
experimental feature. 

gwde-dfdl-experience-7-emptyElementParsePolicy.docx 

This describes the feature as we have implemented it in Daffodil. There 
has been some discussion on this proposal already, particularly on whether 
the enum values for the property are appropriately chosen so that they 
clearly identify the different behaviors. 

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 
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