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

 Hi, All

I am a software engineer and encounter 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%23dt-expanded-qname>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.

could anyone   give me some clarification on this?  Thanks a lot in advance!