The node-test portion of a location step identifies the type of node(s), or the specific node(s), which make up the baseline collection of nodes from which to gather possible matches. It takes three possible forms:
comment()
selects element nodes;text()
selects attribute nodes;processing-instruction()
selects processing instruction nodes;node()
selects nodes of any kind.processing-instruction("target")
to select processing instructions with a particular target.