XPath against a Document

Using Xerces and Xalan;
    given a Document (i.e. DocumentImpl) and given a String containing
an XPath expression, I would like to apply the expression against the
document to obtain the NodeList that matchs the expression.  Is this
possible ?

begin:vcard 
n:Levin;Paul
tel;work:813-261-8935
x-mozilla-html:FALSE
adr:;;;;;;
version:2.1
email;internet:plevin@xxxxxxx
fn:Paul Levin
end:vcard