The algorithm for computing the canonical form from a float/double value in Schema 1.1 is different from the casting float/double semantics described in the F&O.   This was something that QT and the Schema WG agreed to and it seems to have fallen between between the cracks. 

The F&O rules are:
    *  TV will be an xs:string in the lexical space of xs:double or xs:float that when converted to an xs:double or xs:float under the rules of 17.1.1 Casting from xs:string and xs:untypedAtomic produces a value that is equal to SV, or is "NaN" if SV is NaN. In addition, TV must satisfy the constraints in the following sub-bullets.
          o  If SV has an absolute value that is greater than or equal to 0.000001 (one millionth) and less than 1000000 (one million), then the value is converted to an xs:decimal and the resulting xs:decimal is converted to an xs:string according to the rules above, as though using an implementation of xs:decimal that imposes no limits on the totalDigits or fractionDigits facets.
          o  If SV has the value positive or negative zero, TV is "0" or "-0" respectively.
          o  If SV is positive or negative infinity, TV is the string "INF" or "-INF" respectively.
          o  In other cases, the result consists of a mantissa, which has the lexical form of an xs:decimal, followed by the letter "E", followed by an exponent which has the lexical form of an xs:integer. Leading zeroes and "+" signs are prohibited in the exponent. For the mantissa, there must be a decimal point, and there must be exactly one digit before the decimal point, which must be non-zero. The "+" sign is prohibited. There must be at least one digit after the decimal point. Apart from this mandatory digit, trailing zero digits are prohibited.