XPath 2 sequence item type determination

Can someone please say how to determine the item type of any item in an
XPath 2 sequence, whether it be atomic or nodal, and especially in the case
of atomic items if it is boolean, number or string.

Taken as text (ie. characters) xsd can say if the text looks like boolean,
number or string, but is this the same as the actual item type in the XDM
(i.e. the internal vs external representation of a value).

It seems difficult to determine if an (XPath) item which outputs as the
sequence of characters "true" was actually an XDM boolean or string item.

Thanks for the lists help.

JJohansson