Standard: http://www.w3.org/TR/xslt#element-processing-instruction

processing-instruction

Attributes: name

Standard excerpt:

The xsl:processing-instruction element is instantiated to create a processing instruction node. The content of the xsl:processing-instruction element is a template for the string-value of the processing instruction node. The xsl:processing-instruction element has a required name attribute that specifies the name of the processing instruction node. The value of the name attribute is interpreted as an attribute value template.