Use the <xmlpi> element to identify mentions of processing instruction names, such as
<?piname pi value?>. This element enables more precise semantic searching of the DITA source; it also enables distinct formatting. This element is part of the XML mention domain.
See appendix for information about this element in OASIS document type shells.
+ topic/keyword markup-d/markupname xml-d/xmlpi
While DITA does not define any processing instructions, some applications might use some DocBook processing instructions, such as <xmlpi>dbhtml_bgcolor</xmlpi>.