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September 2020

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clarification needed? dfdl:textNumberCheckPolicy 'strict' - language suggests more strict than ICU libraries
by Mike Beckerle 02 Sep '20

02 Sep '20

Say we have this schema snippet: <xs:element name="SimpleDataFormat"> <xs:complexType> <xs:sequence> <xs:element name="NumStudents" type="xs:nonNegativeInteger" dfdl:textNumberCheckPolicy="strict" dfdl:textNumberPattern="#,###" dfdl:textStandardGroupingSeparator="," dfdl:textStandardDecimalSeparator="." /> </xs:sequence> </xs:complexType></xs:element> This successfully parses the data 1234 Even though textNumberCheckPolicy="strict" and the pattern contains a grouping separator, it still allows data that does not contain grouping separators. That said, we have generally tried to make DFDL's spec match the behavior of the ICU library for parsing numbers based on the textNumberPattern. This library has this to say about strict parsing of numbers: The following conditions cause a parse failure relative to [lax] mode (examples use the pattern "#,##0.#"): - The presence and position of special symbols, including currency, must match the pattern. '+123' fails (there is no plus sign in the pattern) - Leading or doubled grouping separators ',123' and '1,,234" fail - Groups of incorrect length when grouping is used '1,23' and '1234,567' fail, but '1234' passes - Grouping separators used in numbers followed by exponents '1,234E5' fails, but '1234E5' and '1,234E' pass ('E' is not an exponent when not followed by a number) So based on ICU's description of strict, this is the expected behavior. It doesn't say anything about missing grouping separators causing an error. Only that if they do exist then they must be in the right spot. The only thing the DFDL specification mentions regarding strict numbers is this: If 'strict' and dfdl:textNumberRep is 'standard' then the data must follow the pattern with the exceptions that digits 0-9, decimal separator and exponent separator are always recognised and parsed To me, that reads like the decimal separator should always be required in strict mode, so this feels like the ICU behavior and the behavior described in the DFDL specification do not match. And I believe the DFDL behavior was intended to match ICU behavior, so it's possible the DFDL specification needs to be updated. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Owl Cyber Defense | www.owlcyberdefense.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy <http://www.ogf.org/About/abt_policies.php>

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