[DFDL-WG] Spec: Leading skip applied to every repeat of a repeating element [s]
Steve Hanson
smh at uk.ibm.com
Wed Oct 17 04:33:38 EDT 2012
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 at uk.ibm.com
tel:+44-1962-815848
From: Suman Kalia <kalia at ca.ibm.com>
To: Steve Hanson/UK/IBM at IBMGB
Cc: dfdl-wg at ogf.org, dfdl-wg-bounces at 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 at ca.ibm.com
For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html
From: Mike Beckerle <mbeckerle.dfdl at gmail.com>
To: Steve Hanson/UK/IBM at IBMGB
Cc: dfdl-wg at 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 at 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 at uk.ibm.com>
To: dfdl-wg at 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 at 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 at uk.ibm.com
tel:+44-1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 16/10/2012 09:02 -----
From: Suman Kalia/Toronto/IBM at IBMCA
To: Steve Hanson/UK/IBM at IBMGB
Cc: Alex Wood1/UK/IBM at 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 at ca.ibm.com
For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html
From: Steve Hanson/UK/IBM at IBMGB
To: Suman Kalia/Toronto/IBM at IBMCA,
Cc: Alex Wood1/UK/IBM at 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 at uk.ibm.com
tel:+44-1962-815848
From: Suman Kalia/Toronto/IBM at IBMCA
To: Steve Hanson/UK/IBM at 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 at ca.ibm.com
For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html
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