[DFDL-WG] Clarification: empty sequence - how can it be non-zero content length

[Steve Hanson]

Take a sequence that has initiator < and terminator > but is defined as 
empty. It is a processing error if the parser finds any content between < 
and >.

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 at ogf.org
Date:   19/07/2018 17:30
Subject:        [DFDL-WG] Clarification: empty sequence - how can it be 
non-zero        content length
Sent by:        "dfdl-wg" <dfdl-wg-bounces at ogf.org>




Section 14.1 states:

      It is a processing error if the SequenceContent region of an empty 
sequence has non-zero length when parsing.

How is it possible for an empty sequence to have a non-zero length of its 
content region?

I understand it could have delimiters outside the content region, and 
other framing possibly, but the content region has nothing in it then only 
annotations can appear.
Annotations can be property definitions or can be DFDL statements. None of 
those can consume representation bits when parsing, or produce 
representation when unparsing.

So I believe this processing error cannot happen.

If I am correct, the statement about processing error should be dropped.

Also, clearly this statement does not apply to a sequence that carries a 
dfdl:hiddenGroupRef, since the hidden group can contribute to the content 
region. I would not consider a sequence carrying hiddenGroupRef to be 
empty unless the referenced group is also empty. 

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