[DFDL-865] Spec Clarification needed: totalDigits, fractionDigits, and
textNumberPattern Created: 22/Aug/13 Updated: 01/Oct/13 Resolved: 23/Sep/13
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Jessie Chab
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s12
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Jessie Chab
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Description
Message posed to Working Group by Mike:
{noformat}
The spec says that these need to be compatible.
"If the pattern uses digits/fractions then these must match any XML schema facets."
We've fallen into this trap before. Facet constraints are about the logical value, not the physical
rep, and so must make equal sense for binary representations as text representations.
I was considering what kinds of static cross checks would make sense here.
Example: suppose fractionDigits='2'.
Suppose textNumberPattern="##"
the type must be xs:decimal since that's the only type that can have fractionDigits constrained in
DFDL.
Is there a conflict of the facet with the textNumberPattern? I think not. Even though the pattern
doesn't allow for any fractional part to be expressed, that means that all values will have less
than or equal to 2 fractional digits (because no fractional digits always satisfies that.)
Now suppose textNumberPattern="#.########"
Now the textNumberPattern will parse and accept things like 1.234 which have more than 2
fraction digits, but suppose the data simply doesn't contain any such. So all number in the data
will obey the less than or equal to 2 fractional digits.
Lastly, suppose textNumberPattern="9.9999"
So, interpreted naively, this requires the data to contain 5 digits, so this seems inconsistent with
fractionDigits of 2.
However, we know this depends on the strict/lax behavior of ICU libraries, and I believe this
will happily parse the data "0.0" without error. Hence the data could still all have 2 or fewer
fractional digits.
So, I think this idea that the totalDigits and fractionDigits facets can be cross-checked with the
textNumberPattern is spurious and we should drop it.
I think it dates from a time when we were still confused about the separation of the DFDL
Infoset, and facet constraints on its value spaces, which are abstract, versus the XML Infoset,
where everything truly is a string as well as whatever its XML Schema type says.{noformat}
Comments
Comment by Mike Beckerle [ 23/Sep/13 ]
This was clarified, and the spec as of Sept 2013 (v1.0.4), no longer requires any consistency
checking between totalDigits, fractionDigits, and textNumberPattern.
Note that for validation, fractionDigits applies only to xs:decimal type, where it is meaningful
for both text and binary representations.
Comment by Mike Beckerle [ 23/Sep/13 ]
This was just a issue to get a resolution from the DFDL workgroup to a question on the spec.
That clarification is now in the spec, or rather the confusing requirement to cross check
textNumberPattern and fractionDigits has been dropped.
Comment by Jessie Chab [ 01/Oct/13 ]
verified change in spec, marked requirement as obsolete in Testlink, modified tests to expect a
correct parse and validation errors. Moved tests from scala-debug to scala, updated test
descriptions, and marked as 'passed' in testlink.
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