In the XML representation for simpleType, final is shown as 

final = (#all | (list | union | restriction)) 

This would seem to imply that only 1 of {list, union, restriction} may be 
specified. 

However, the description of the property is as follows: 

A set corresponding to the actual value of the final [attribute], if present, 
otherwise the actual value of the finalDefault [attribute] of the ancestor 
schema element information item, if present, otherwise the empty string, as 
follows: 

the empty string 
  the empty set; 
#all 
  {restriction, list, union}; 
otherwise 
  a set with members drawn from the set above, each being present or absent 
depending on whether the string contains an equivalently named space-delimited 
substring. 

Given this, is it, or is it not possible to restrict 2 of {restriction, list, 
union}?