a bit of information meant for the application using the XML document
Used in an XML document to embed information intended for proprietary applications. An example of a processing instruction is ?word document="test.doc" ?.
Directions that allow XML authors to send instructions directly to a processing that may be outside the native capacities of XML. A processing instruction is differentiated from normal element markup by question marks after the opening and before the closing (i.e. ? Instruction ? ). The XML declaration is itself a processing instruction.