[DFDL-WG] Action 185: Text number rounding and ICU

[Steve Hanson]

As described in action 185, the DFDL spec behaviour for the DFDL 
properties that control text number rounding was derived from the 
documented behaviour for ICU4J. However the documentation is not correct 
and the ICU4J behaviour is as described for ICU4C.  An ICU ticket was 
raised to clarify the position, and the intended behaviour is the observed 
behaviour. That affects the DFDL text number rounding properties as 
follows:

textNumberRounding
Enum
Specifies how rounding is controlled during unparsing.
Valid values ‘pattern', 'explicit'
When dfdl:textNumberRep is 'standard' this property only applies when 
dfdl:textStandardBase is 10.
If 'pattern' then rounding takes place according to the pattern. A 
rounding increment may be specified in the dfdl:textNumberPattern using 
digits '1' though '9', otherwise rounding is to the width of the pattern. 
The rounding mode is always 'roundHalfEven'. 
If 'explicit' then the rounding increment is specified by the 
dfdl:textNumberRoundingIncrement property, and any digits '1' through '9' 
in the dfdl:textNumberPattern are treated as digit '0'. The rounding mode 
is specified by the dfdl:textRoundingMode property. 
To disable rounding, use 'explicit' in conjunction with 'roundUnnecessary' 
for the dfdl:textNumberRoundingMode. If rounding is disabled then any 
excess precision is treated as a processing error. 
Annotation: dfdl:element, dfdl:simpleType
textNumberRoundingMode
Enum
Specifies how rounding occurs during unparsing, when 
dfdl:textNumberRounding is 'explicit'.
When dfdl:textNumberRep is 'standard' this property only applies when 
dfdl:textStandardBase is 10.
To switch off rounding, use 'roundUnnecessary'. 
Valid values ‘roundCeiling’,  ‘roundFloor’, ‘roundDown’, ‘roundUp’, 
‘roundHalfEven’,  ‘roundHalfDown’, ‘roundHalfUp', 'roundUnnecessary'
Annotation: dfdl:element, dfdl:simpleType
textNumberRoundingIncrement
Double
Specifies the rounding increment to use during unparsing, when 
dfdl:textNumberRounding is 'explicit'.
When dfdl:textNumberRep is 'standard' this property only applies when 
dfdl:textStandardBase is 10.
To switch off rounding, use 0.0. 
A negative value is a schema definition error.
Annotation: dfdl:element, dfdl:simpleType
 
Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh at uk.ibm.com
tel:+44-1962-815848
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 
741598. 
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU

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