[DFDL-WG] Spec question: 16.6 Forward Progress Requirement

[Tim Kimber]

16.6 Forward Progress Requirement 
It is a processing error when an array is potentially unbounded and the 
position in the data does 
not move during the parsing of an occurrence of the element including any 
associated separator. 
This is to prevent an infinite loop. An array is potentially unbounded if 
any of the following are 
true: 
* dfdl:occursCountKind is 'parsed' or 'stopValue' 
* dfdl:occursCountKind is 'implicit' and XSDL maxOccurs is 'unbounded'

Q1: Is this paragraph intended to 
a) safely terminate the parsing of the array, allowing the parser to 
proceed with whatever follows in the DFDL schema or
b) cause the parser to discard the entire array along with everything that 
was parsed within the nearest point of uncertainty?
If b) then I think a Schema Definition Error would be more appropriate ( 
because backing out the entire array implies that none of the occurrences 
were well-formed and some later branch might be the correct option ). 
Although...

Q2: If the array has occursCountKind='stopValue' then none of the 
occurrences is an actual point of uncertainty because only stopValue can 
terminate the array. If paragraph 16.1 is invoked then a processing error 
will be thrown. But the occurrence is not a point of uncertainty so the 
entire array will be treated as badly-formed. In other words, behaviour 
will be as described in option b) above. I think that is correct in this 
case because the array's stopValue was never found.

Q3: Should this infinite-loop detection be performed only after at least 
minOccurs occurrences of the array have been processed successfully? Until 
then, I think an empty occurrence should cause the default value to be put 
into the info set.

regards,

Tim Kimber, DFDL Team,
Hursley, UK
Internet:  kimbert at uk.ibm.com
Tel. 01962-816742 
Internal tel. 37246742

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