Using qxmlpatterns

[kitten]

hi to everyone
i want to use qxmlquery and the others to parse some information i got in program
i know the style of xml data is like this
@<key xsi:type="xsd:string">message</key><value xsi:type="xsd:string">Username or/and Password doesnt match.</value>@
how can i use qxmlpatterns library to parse this?