<xsd:documentation>Representation of a number as a double, possibly qualified as a ratio of doubles.
Ratio component attributes 'numerator' and 'denominator' may be both present or both absent.
When ratio component attributes are present, the ratio represented is to be used with
the double representation included for human readability.
A 'canonical' representation, according to the following rules, is suggested:
Only use numerator/denominator when the representation of the number as double is not
sufficiently precise (i. e. causes errors of accumulation).
Express both numerator and denominator as integers (doubles with integer values) reduced
to 'least common denominator' if possible.</xsd:documentation>