Default/fixed values for xsi:type and xsi:nil
xsi:type must resolve to a type definition
xsi:type must resolve to a type definition
When an xsi:type attribute appears on an element, and has a QName as its value,
but the QName does not resolve to a known type definition, processors are now
required to "fall back" to lax validation, using the declared {type definition}
of the governing element declaration as the governing type definition.
Structures introduces a mechanism for signaling that an element
must be accepted as 'valid' when it has no content despite a content type which
does not require or even necessarily allow empty content. An element can be 'valid'
without content if it has the attribute xsi:nil with the value true. An element
so labeled must be empty, but can carry attributes if permitted by the corresponding
complex type.
default values for xsi:nil