[DFDL-WG] clarification needed: setVariable - executes before or after framing of the element/model group

[Steve Hanson]

Mike

>From section 9.5:

For sequences, choices and group refs: 
1.      dfdl:discriminator or dfdl:assert(s) with testKind 'pattern' 
(parsing only) 
2.      dfdl:newVariableInstance(s) - in lexical order, innermost schema 
component first 
3.      dfdl:setVariable(s) - in lexical order, innermost schema component 
first
4.      dfdl:sequence or dfdl:choice or dfdl:group following property 
scoping rules
5.      dfdl:discriminator or dfdl:assert(s) with testKind 'expression' 
(parsing only) 

This says that a setVariable on a group is processed before the format 
annotations of the group, so your example would be allowed.

For discriminators and asserts, when they are executed depends of the 
testKind. If 'pattern' they are executed first. If 'expression' they are 
executed last. 

All seems clear to me - am I missing some subtlety somewhere?

Regards
 
Steve Hanson
IBM Integration Bus, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890



From:   Mike Beckerle <mbeckerle.dfdl at gmail.com>
To:     "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>
Date:   02/09/2016 16:56
Subject:        [DFDL-WG] clarification needed: setVariable - executes 
before or after framing of the element/model group
Sent by:        "dfdl-wg" <dfdl-wg-bounces at ogf.org>




The spec defines where setVariable executes as a statement relative to 
element processing and model-group processing.

Question is: what does element and model group processing mean: the value 
region of the element, the content region of the element,  or the whole 
element including all framing?

So, for an element, spec says that setVariables run after the element.

Rhetorical question: Does "after" mean after the terminator (including any 
expression for the terminator) has completed?

Yes, because otherwise a element could contain the value of its own 
terminator, and that wouldn't work for lengthKind='delimited' as you would 
need the value to get the terminator to parse the value. 

So 'after' has to mean after the terminator, meaning all framing, and any 
other expression that can affect the length or interpretation in forming 
the element.

For a model group, the spec says that setVariables run before the model 
group.

So, can a sequence carry a set-variable that sets a variable value that is 
then used in the initiator property of that very sequence?

E.g.,

<xs:sequence dfdl:initiator="{ $init }">
   <xs:annotation><xs:appinfo ...>
       <dfdl:setVariable ref="init">{ ../someplace/else 
}</dfdl:setVariable>
  </xs:appinfo></xs:annotation>
   ..... reset of sequence
</xs:sequence>

If this is not allowed for the initiator, what about for the terminator or 
separator, or outputNewLine or encoding or any other property that
affects the syntax of the model group? 

What about discriminators/asserts. Do those run before the sequence's 
initiator is matched, or after? E.g., can a discriminator indicate "true", 
but then the initiator fails to match?

When unparsing, you don't execute discriminator/assert at all, so no 
guidance there. 

Maybe this is clear already, but I am not sure if setVariables should run 
before any framing of a model group, or after the framing, but before the 
content region, or before the value region.

...mikeb

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | 
www.tresys.com
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