[XQuery] MS-XQ-LC1-056

Section 3.2 Path Expressions	
Technical	

fn:root(self::node()) treat as document-node() is not precise enough for
meaningful static typing of path expressions of the form /a/b/c. We
should use a type that is given via the static context as a new property
such as the static type of a built-in context root item (similar to the
notion of a context item).