[DFDL-WG] Need clarity: when unparsing dfdl:length expression is evaluated or not?

[Mike Beckerle]

Ok, I found erratum 5.18 which is clear about this. I had to download the
latest version.

This matter is closed. Yes the dfdl:length expression IS evaluated for
dfdl:lengthKind 'explicit'.

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
www.tresys.com
Please note: Contributions to the DFDL Workgroup's email discussions are
subject to the OGF Intellectual Property Policy
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On Thu, May 7, 2015 at 10:27 AM, Mike Beckerle <mbeckerle.dfdl at gmail.com>
wrote:

> Digging through the minutes of calls this year I found this statement in
> https://redmine.ogf.org/issues/258 which is the resolution of action 276.
>
> "WG agreed to reverse erratum 2.100. The original variable length
> behaviour scenario that motivated 2.100 in the first place can still be
> achieved using outputValueCalc with dfdl:valueLength(). Spec will revert to
> describing lengthKind 'explicit' as fixed length for both literal and
> expression lengths."
>
> I think this means dfdl:length expressions are evaluated to get the length
> even when unparsing.
>
> We need to flat out say that someplace. It's way too hard to find this
> statement.
>
>
> Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
> www.tresys.com
> Please note: Contributions to the DFDL Workgroup's email discussions are
> subject to the OGF Intellectual Property Policy
> <http://www.ogf.org/About/abt_policies.php>
>
>
> On Thu, May 7, 2015 at 10:12 AM, Mike Beckerle <mbeckerle.dfdl at gmail.com>
> wrote:
>
>> I know we discussed this extensively, and there are notes that the IBM
>> DFDL implementation evaluates a dfdl:length expression when unparsing.
>>
>> But searching the mail history, the trackers, etc. I cannot find a clear
>> definitive statement of what we finally decided as to whether this is the
>> official behavior or not.
>>
>> I cannot find language in the DFDL spec that says that the dfdl:length
>> expression is or is not evaluated.  (No such problem for
>> dfdl:occursCountKind 'expression'. There we are very clear it is NOT
>> evaluated when unparsing.)
>>
>> There is this statement in the discussion of dfdl:contentLength function:
>>
>> "When unparsing with dfdl:lengthKind "explicit", the calculation of
>> dfdl:contentLength() returns the value of the dfdl:length property."
>>
>> It does not say whether this forces the expression (if dfdl:length is an
>> expression) to be evaluated or not, though it implies it must be evaluated
>> because otherwise it would be undefined in that situation.
>>
>> Is this the only situation during unparsing when the dfdl:length
>> expression is evaluated?
>>
>> ...mike
>>
>> Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
>> www.tresys.com
>> Please note: Contributions to the DFDL Workgroup's email discussions are
>> subject to the OGF Intellectual Property Policy
>> <http://www.ogf.org/About/abt_policies.php>
>>
>>
>
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