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

[Mike Beckerle]

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
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