Lack Of Definition Of A Valid Ratio (part of detailed review of common microsyntaxes)

The ratio subsection of common microsyntaxes does not do what the  
rest of the numbers do: define what a valid number is. Due to the  
algorithm returning at all sorts of places, it is rather complex to  
work out, but I think:

[[
A string is a valid ratio if it consists of either one of more  
characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE  
(9) followed by a denominator punctuation character (see table  
below), or two valid unsigned integers separated by one or more  
characters in Unicode character class Zs.
]]

- Geoffrey Sneddon