·        to determine if an element declaration or reference is scalar or array

·        to determine the required minimum number of occurrences of an array both when parsing and unparsing

Section 16.13
( Note : this definition of 'required' is a repeat of the defintion in section 3 )
Definition: 'required'
We define the term 'required' as follows:
·        A scalar element is required.
·        An element of a fixed-occurrence array is required.
·        An element of a variable-occurrence array is required if its index is less than or equal to the value of minOccurs.
All other elements are not required.
...

On unparsing, if an element is required, and is not part of the logical data and the element has a default value specified then it is used, otherwise it is a processing error.

Section 17.3.1 : Sequence groups and separators

re: the combination of separatorPolicy="suppressAtEnd" and sequenceKind="ordered":
All separators must be found in the data except that when the sequence has trailing optional items, the separators are suppressed for any final missing items. Note suppressAtEnd can only be used when there is no clash with delimiters from the containing structure.

My interpretation of the specification is:
a) if separatorPolicy="require" then the unparser should output a separator for all missing required elements ( whether array members or not )
b) if separatorPolicy="suppressAtEnd" then the unparser should output a separator for all non-trailing missing required elements
c) separators for missing elements must be output regardless of whether the element is required/optional, simple/complex, does/does not have a default value etc. I assume this because the term 'missing' is used rather than the very clearly-defined term 'required'.

Reading between the lines, I also infer the following rules:
d) if an array has maxOccurs="unbounded" and it is missing from the infoset then the unparser will not output any separators for the array
e) if an array has maxOccurs!="unbounded" and it is missing from the infoset then  the unparser will output a separator for each missing occurrence ( so it will output maxOccurs separators ).
f) if an element contains a child group, and none of the group members are present in the infoset, then the group is 'missing' and the unparser will output a separator for it.

Suggested changes to the specification:
- As a minimum, I think it would be useful for the specification to include a definition of 'missing'.
- DFDL does not allow min/maxOccurs on groups, so they implicitly have cardinality 1:1. Specification should specify the behaviour of the unparser when none of a group's members are present in the infoset.
- The wording in 17.3.1 could be more accurate. I don't think the word 'optional' should be there ( if validation is off then the unparser will tolerate missing required elements ). I think the words 'trailing' and 'final' are intended to mean the same - we should standardize on 'trailing'.

regards,

Tim Kimber, Common Transformation Team,
Hursley, UK
Internet:  kimbert@uk.ibm.com
Tel. 01962-816742  
Internal tel. 246742

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