Open content is implemented.
The allows a complex type to specify open content with mode "interleaved" or "suffix", allowing arbitrary elements (satisfying a wildcard) to be added either anywhere in the content sequence, or at the end.
At the level of a schema document, the defaultOpenContent defines the default open content mode
for all types defined in the schema document (or, for all types except those with an empty content model).
Similarly, the defaultAttributes attribute of the xs:schema element defines
a default attribute wildcard to be permitted for all complex types defined in the schema document.
