[DFDL-WG] Action 261

[Tim Kimber]

Implied separatorSuppressionPolicy for occursCountKind Implied 
separatorSuppressionPolicy for occursCountKind ''''expression expression 
expression '''' (All)
10/6: Spec says it is 'never' (positional sequence) but you have to parse 
to identify the position, so isn't that non-positional?

I think there are two alternative definitions of 'positional':
a) the identity of every delimited field is known before parsing of the 
sequence group begins
b) the identity of every delimited field is known before parsing of the 
field begins

As an implementer, b) is sufficient because it means that the parser never 
needs to backtrack while parsing the group. 
a) allows the field identities to be statically known, but that is less 
important - it does not allow optimised extraction of a particular field 
as would be the case for a fixed-length group ( the possibility of escaped 
separators/terminators means that every character will need to be scanned 
anyway ).

It may sound like a small point, but it affects two decisions
1. whether ock='expression' should be allowed within a positional sequence 
group ( action 261 )
2. what the behaviour of the unparser should be w.r.t. ock='expression'.

My own feeling is that ock='expression' should be treated almost exactly 
like ock='fixed', except that the calculated array length N is used 
instead of maxOccurs.
- When parsing a positional sequence group it should cause N delimiters to 
be expected for the array.
- When unparsing a positional sequence group it should cause N delimiters 
to be written.
These rules are consistent and straightforward to describe and implement. 
The current rule ( unparser outputs the occurrences that are in the info 
set only ) allows the unparser to write a document that cannot be parsed 
using the same schema.

regards,

Tim Kimber, 

----- Forwarded by Tim Kimber/UK/IBM on 10/06/2014 20:34 -----

From:   Steve Hanson/UK/IBM at IBMGB
To:     dfdl-wg at ogf.org, 
Date:   10/06/2014 17:57
Subject:        [DFDL-WG] OGF DFDL WG Call Minutes 2014-06-10
Sent by:        dfdl-wg-bounces at ogf.org



Please find minutes from the above call at 
http://redmine.ogf.org/dmsf_files/13263?download= 

Regards

Steve Hanson
Architect, IBM DFDL,
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh at uk.ibm.com
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