XPath "validation"

Given

(1) an XML schema (expressed in any schema language, though my strong
preference would be RNG/C)

and

(2) an XPath path expression (whether XPath 1.0 or 2.0),

it should be possible to compute the "possibility" of the path expression's
finding anything in an XML document that is valid under the schema, understood
as one of the three following values:

* Guaranteed
* Possible
* Impossible

Question: Does there exist any software to compute "possibility" in this way?
Or anything like it? Or anything like it for any other restricted set of XPath
expressions?

Related question: Does there exist software that infers schema information
from XPath expressions?

"Software" here doesn't have to be commercial, or much more than just some
researcher's script collection. :)

Norm Birkett