Mike
dfdl:lengthUnits is not currently used by
dfdl:choice. If by erratum we changed this, existing schemas could break
as they would suddenly pick up the value from scope. We have a couple of
alternatives:
1) A new property dfdl:choiceLengthUnits
with enums 'bytes' and 'bits' (not seen a use case for 'characters'). For
compatibility, an implementation would need to default the value to 'bytes'
if not set locally or in scope, rather than give an error. **
2) New enum for dfdl:choiceLengthKind 'explicitBits'
which causes the dfdl:choiceLength to be interpreted as a bit count. Avoids
the default pitfall, but is architecturally inconsistent with lengthKind/length/lengthUnits.
** IBM DFDL had to do a similar thing when
dfdl:encodingErrorPolicy was added to avoid breaking existing schemas.
Alternative is to bump the DFDL version number.
Regards
Steve Hanson
IBM Hybrid Integration, 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:
15/12/2016 16:04
Subject:
[DFDL-WG] spec
bug dfdl:choiceLength says 'bytes' should use dfdl:lengthUnits
Sent by:
"dfdl-wg"
<dfdl-wg-bounces@ogf.org>
for dfdl:choiceLength, the description says "Specifies
the length of the choice in bytes..." clearly this should use dfdl:lengthUnits.
We have tons of cases where byte granularity is not sufficient,
and this is hard to work around. You have to use dfdl:choiceLengthKind='implicit'
and then carefully pad the branches to the same length in bits. It's painful.
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology
| www.tresys.com
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