Pattern facets and round trips.
If you are defining a schema that has elements or attribute of numeric types and require more restrictions on their value, try to avoid using pattern facets. If you do, you will get the warning:
Warning: Type (name of your type) is restricted by a facet 'pattern'
that may impede full round-tripping of instances of this type.
You may end up doing this because you want to specify that the number start with the digit 1 and end with the digit 9. Of course, this isn't a common scenario and you are more likely to want a certain number of digits or a minimum or maximum value. In those case, use the minInclusive, minExclusive, maxInclusive and maxInclusive facets.
