After installation you should be able to execute domxml and saxxml, which can be used to check whether the XML parsing subsystem actually works:

$ cd SOPE/sope-xml/samples
$ saxxml data/slashdot.rss
start document ..
ns-map: rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#
ns-map: dc=http://purl.org/dc/elements/1.1/
...

This should print out the processed XML tree. If it reports a missing XML parser, something is broken.