Hi,
http://www.cisco.com/en/US/partner/products/sw/custcosw/ps1846/products_user_guide_list.html
You are looking for the "Scripting and Development Series" for your particular UCCX version.
Er... the XML section is er... fuzzy. You'll see.
To sum it up: UCCX can read an XML file from the local document repository or from a HTTP URL and perform an XPath query.
For advanced users, there's also a possibility of an XSL transforming an XML document.
G.