[DFDL-WG] public comment "Non-deterministic outcome of setVariable evaluations" (Action 229)

[Mike Beckerle]

Revised proposal that fully specifies evaluation order for setVariable and
newVariableInstance.

---------------------------------------------

Errata 3.20, 3.21, and Errata 3.25 must be modified (and the corresponding
sections of the spec)

For errata 3.20, and errata 3.21 the sentence:

 "However, the order of execution among them is not specified. Schema
authors can insert sequences to control the timing of evaluation of
statements more precisely."

is replaced by:

"The order of execution is specified in errata 3.25."

Errata 3.25 is modified.

Numbered item 3 of both the first list and second list is replaced by:

3. dfdl:setVariable(s) - in lexical order, innermost schema component first

Numbered item 2 of the second list is replaced by:

2. dfdl:newVariableInstance(s) - in lexical order, innermost schema
component first

These two paragraphs are added below the numbered lists to clarify what
'lexical order, innermost schema component first' means.

The dfdl:setVariable annotations at any one annotation point of the schema
are always executed in lexical order. However, dfdl:setVariable annotations
can also be found in different annotation points that are combined into the
resolved set of annotations for one schema component. In this case, the
order of execution of the dfdl:setVariable statements from any one
annotation point remains lexical. The order of execution of the
dfdl:setVariable annotations different annotation points follows the
principle of innermost first, meaning that a schema component that
references another schema component has its dfdl:setVariable statements
executed after those of the referenced schema component. For example, if an
element reference and an element declaration both have dfdl:setVariable
statements, then those on the element declaration will execute before those
on the element reference. Similarly dfdl:setVariable statements on a base
simple type execute before those of a simple type derived from it. The
dfdl:setVariable statements on a simple type execute before those on an
element having that simple type (whether by reference, or when the simple
type is lexically nested within the element declaration). The
dfdl:setVariable statements on the sequence or choice within a global group
definition execute before those on a group reference.

The dfdl:newVariableInstance annotations at any one annotation point of the
schema are always executed in lexical order. However,
dfdl:newVariableInstance annotations can also be found in different
annotation points that are combined into the resolved set of annotations
for one schema component. In this case, the order of execution of the
dfdl:newVariableInstance statements from any one annotation point remains
lexical. The order of execution of the dfdl:newVariableInstance annotations
different annotation points follows the principle of innermost first,
meaning that a schema component that contains or references another schema
component has its dfdl:newVariableInstance statements executed after those
of the contained or referenced schema component. For example, if a group
reference and the sequence or choice group of a group definition both have
dfdl:newVariableInstance statements, then those on the global group
definition will execute before those on the group reference.

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