Hi Mike
As will be minuted, we agreed on the WG call today that we disallow
expressions that return empty string for properties where empty string
turns off the property. Please can you take a look through the spec and
see if any properties other than initiator, terminator, separator are
impacted, then I can complete the errata.
(I would expect that inputValueCalc and outputValueCalc are not affected
by this errata, as empty string is a legal value for the element in
question if it is of type xs:string).
Regards
Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
From: Mike Beckerle
To: dfdl-wg@ogf.org
Date: 10/01/2012 08:06
Subject: [DFDL-WG] spec clarification needed: is dfdl:terminator='{
...returns empty string ... }' allowed?
Sent by: dfdl-wg-bounces@ogf.org
Let's use the example of terminator as a delimiter.
If I provide an expression so that I can compute terminator at runtime, is
it allowed to return empty string? I.e., equivalent to writing
dfdl:terminator="" which is effectively "turning off" use of terminator?
It seems very problematic to me if we allow this. Nor do I think this
generality is needed.
We should clarify that for initiator/terminator/separator, if a runtime
expression is used, then it must return at least one non-zero-length
value. So using a runtime expression for a delimiter is effectively saying
"yes there will be a delimiter", you are just not binding its specific
value.
I believe this runtime expression capability for delimiters was intended
to allow the choice of the specific delimiter to be made based on data
containing the value. This is common practice in data formats.
However, turning on/off whether delimiters are present or not, is not
something I anticipated, and it has far bigger implications for the
format. I mean you really can't decide much about the data format
statically if even the existence of delimiters as part of the format or
not can be postponed to runtime.
Comments?
--
Mike Beckerle | OGF DFDL WG Co-Chair
Tel: 781-330-0412
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