Try:
names of nodes of usb plane of iokit registry
iokit and plist relevance is odd. If it gives an error stating The operator "string" is not defined, then it is not returning nothing, it is in fact returning something, it just doesn’t know how to display a string representation of it.
It took me a while to figure out where QnA is located in OS X. I was on a new machine that didn’t have the old app version of QnA installed, so I created this relevance to help:
https://bigfix.me/relevance/details/3006012
pathnames of (files "/Library/BESAgent/BESAgent.app/Contents/MacOS/QnA"; files "/usr/local/bin/QnA"; files "/opt/BESClient/bin/qna")