Actions 290 and 291 raised to investigate further
- see minutes.
Regards
Steve Hanson
IBM
Integration Bus, Hursley, UK
Architect, IBM
DFDL
Co-Chair, OGF
DFDL Working Group
smh@uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
From:
Steve Hanson/UK/IBM
To:
Mike Beckerle <mbeckerle.dfdl@gmail.com>
Cc:
"dfdl-wg@ogf.org"
<dfdl-wg@ogf.org>
Date:
13/09/2016 13:14
Subject:
Re: [DFDL-WG]
Suggest should be optional feature of DFDL - dfdl:utf16Width='variable'
and other corner cases
Mike
I am assuming that the processing for utf-16
'fixed' or 'variable' is entirely handled by ICU so there should be no
coding overhead.
IBM DFDL works ok for dfdl:lengthKind='explicit'
for an element of complex type with dfdl:lengthUnits='characters' and dfdl:encoding="utf-8".
But there are conditions the content of the complex type must satisfy otherwise
an SDE results, such as:
CTDV1524E : For a complex element, when
'lengthKind' is 'explicit' or 'prefixed', and 'lengthUnits' is characters,
all simple child elements must have text representation, 'lengthUnits'
set to 'characters' and the same encoding.
So we insist that the properties of the children
are consistent with the properties of the parent. If you recall,
IBM DFDL does all these kinds of validation checks in a pre-processing
phase.
That seems a pretty sensible rule but I am
not sure if the rule appears in the spec as such - I just had a quick look
but didn't spot anything.
So I guess I don't see a need for these things
to be optional features?
Regards
Steve Hanson
IBM
Integration Bus, Hursley, UK
Architect, IBM
DFDL
Co-Chair, OGF
DFDL Working Group
smh@uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
From:
Mike Beckerle <mbeckerle.dfdl@gmail.com>
To:
"dfdl-wg@ogf.org"
<dfdl-wg@ogf.org>
Date:
10/08/2016 18:57
Subject:
[DFDL-WG] Suggest
should be optional feature of DFDL - dfdl:utf16Width='variable' and other
corner cases
Sent by:
"dfdl-wg"
<dfdl-wg-bounces@ogf.org>
Given the limited set of required encodings for a conforming
DFDL processor, I believe dfdl:utf16Width='variable' should be an optional
feature.
That's just consistency with what is optional already.
But it is also quite hard to implement.
There are other situations that are very hard to implement,
probably never used by real users, yet which are non optional in the spec:
I would suggest that dfdl:lengthKind='explicit' for elements
of complex type, with dfdl:lengthUnits='characters' and a variable-width
encoding like utf-8 is very problematic to implement. I am pretty sure
IBM DFDL has no implementation of this per email threads, and I know I
don't want to implement this in Daffodil even though we're trying to be
very comprehensive in the implementation eventually.
I think implementations should be free to just not implement
this. These sorts of cases often exist just because we're trying
to preserve some orthogonality of composition in the language. So it's
possible to do quite a few things that probably aren't ever needed by anyone,
that reflect ill-defined data formats, etc.
I'd rather not document a bunch of "non-conformances"
for Daffodil or other implementations for these sorts of things. I'd like
to say we don't implement them, but they're optional, and so that's allowed.
Comments?
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology
| www.tresys.com
Please note: Contributions to the DFDL Workgroup's email
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Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU