It is certainly true that the DFDL philosophy is that you wrap a repeating element if you want to specify framing that applies to the array as a whole. Array separator, initiator, terminator, leadingSkip, alignment and trailingSkip are all consistent in this respect, so it does seem wrong to change leadingSkip to behave in a different way.

For leadingSkip, there is an alternative to wrapping the repeating element in a sequence, you could instead insert an empty sequence immediately before the repeating element.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848

From: Suman Kalia <kalia@ca.ibm.com>
To: Steve Hanson/UK/IBM@IBMGB
Cc: dfdl-wg@ogf.org, dfdl-wg-bounces@ogf.org
Date: 16/10/2012 23:03
Subject: Re: [DFDL-WG] Spec: Leading skip applied to every repeat of a repeating element [s]

The DFDL approach will work for COBOL case but it would require wrapping the repeating element having such alignment requirement in a dummy sequence. Not very good from a logical model point of view but certainly will be consistent with other DFDL properties..

Suman Kalia
IBM Canada Lab
WMB Toolkit Architect and Development Lead
Tel: 905-413-3923 T/L 313-3923
Email: kalia@ca.ibm.com

For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html

From: Mike Beckerle <mbeckerle.dfdl@gmail.com>
To: Steve Hanson/UK/IBM@IBMGB
Cc: dfdl-wg@ogf.org
Date: 16/10/2012 13:45
Subject: Re: [DFDL-WG] Spec: Leading skip applied to every repeat of a repeating element [s]
Sent by: dfdl-wg-bounces@ogf.org

I would assume that the skip properties are not array-oriented, as they don't have "occurs" in their name. Hence, they apply to each element instance in the same way as lengthKind and encoding and other non "occurs" properties.

....mike

From: Steve Hanson <smh@uk.ibm.com>
To: dfdl-wg@ogf.org,
Date: 10/16/2012 04:18 AM
Subject: [DFDL-WG] Spec: Leading skip applied to every repeat of a repeating element [s]
Sent by: dfdl-wg-bounces@ogf.org

Need confirmation from the DFDL WG as to the purpose of the leadingSkip property. The grammar says that leadingSkip applies to all occurrences of an array element. Suman has indicated (below) that his intent for the property was to apply to the array as a whole. The DFDL approach for 'array as a whole' properties is to carry them on a wrapper sequence, not the element itself.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 16/10/2012 09:02 -----

From: Suman Kalia/Toronto/IBM@IBMCA
To: Steve Hanson/UK/IBM@IBMGB
Cc: Alex Wood1/UK/IBM@IBMGB
Date: 15/10/2012 22:58
Subject: Re: [Work Item 9791] Spec: Leading skip applied to every repeat of a repeating element [s]

I intended the behavior of leading and trailing skip counts for repeats to be same as in MRM. I can't say for sure if this would break anything in PL/1 as we have not implemented but certainly this behavior is required for COBOL.. We can discuss this in workgroup and if everyone agrees add it to Errata..

Suman Kalia
IBM Canada Lab
WMB Toolkit Architect and Development Lead
Tel: 905-413-3923 T/L 313-3923
Email: kalia@ca.ibm.com

For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html

From: Steve Hanson/UK/IBM@IBMGB
To: Suman Kalia/Toronto/IBM@IBMCA,
Cc: Alex Wood1/UK/IBM@IBMGB
Date: 10/15/2012 01:24 PM
Subject: Re: [Work Item 9791] Spec: Leading skip applied to every repeat of a repeating element [s]

Does that mean in MRM that we have asymmetric behaviour between leadingSkip and trailingSkip ? I'm reading that for MRM leading skip was just for first element, but trailing skip is for every repeat. That's not how the DFDL grammar says things work - it applies leading skip to every repeat.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848

From: Suman Kalia/Toronto/IBM@IBMCA
To: Steve Hanson/UK/IBM@IBMGB
Date: 15/10/2012 15:18
Subject: Re: [Work Item 9791] Spec: Leading skip applied to every repeat of a repeating element [s]

I am travelling and offsite and cannot access the RTC..

Yes trailing skip count get applied to every repeating element.. this is the same semantic we have in MRM.. In COBOL terms , these are slack bytes which are added at the end of the structure if required.

Suman Kalia
IBM Canada Lab
WMB Toolkit Architect and Development Lead
Tel: 905-413-3923 T/L 313-3923
Email: kalia@ca.ibm.com

For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html

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