Targeted Processing Instruction Tests
A node test can be a processing instruction that specifies a target. The syntax for such a node test is as follows:
processing-instruction("target")
By specifying a target, the processing instruction test locates all the processing instruction nodes that match that target. For example, the following node test locates all the processing instruction nodes in a document that specify an XSLT file.
/child::processing-instruction("xml-stylesheet")