XSLT and XPATH: A Guide to XML Transformations

6.7. Comments and Processing-Instructions

There are two XSLT instruction elements that create what is considered content internal to the output XML document. Normally, internal content is not intended for end users. This internal content can be in the form of XML processing instructions, or XML comments. Processing instructions, or PIs, and comments are embedded in the output XML document as part of the document structure, but are not considered part of the document content, and cannot be seen by most rendering engines.

Processing instructions generated with <xsl:processing-instruction> are used by an external process, identified by the target of the PI, to handle the XML file in a specific way, based on the parameters of the PI. Comments generated ...