FW: A quesiton on XPath-datamodel (Mapping PSVI addition to Node Properties)

I encountered some problem when reading the spec of XQuery 1.0 and XPath
2.0 Data Model (XDM).

http://www.w3.org/TR/xpath-datamodel/#PSVI2Types

In the Chapter 3.3.1 ( Mapping PSVI addition to Node Propterties), it
says:

*	The [validity] and [validation attempted] properties exist and
have the values "valid" and "full", respectively, the schema type of an
element or attribute information item is represented by an
expanded-QName
<http://www.w3.org/TR/xpath-datamodel/#dt-expanded-qname#dt-expanded-qna
me>  whose namespace and local name correspond to the first applicable
items in the following list:

	*	If the declared type exists and is a union and the
actual type is .....
	*	If there is no declared type, and the actual type is a
union, then: ......
	*	Otherwise: ......

 

Regarding the second bullet, I can NOT understand in which cases there
will be no declared type?  I think it is impossible. Since the declared
type reference the [type definition] associated with the declaration,
if an element/attribute is validated, it should be already associated
with a element/attribute declaration, which should have the type
definition. 

 

Does anyone know it and  give me some clarification on this?  Thanks a
lot in advance!