Rename a processing instruction with XSL

I would like to rename a processing instruction in xsl. My input looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<material xml:lang="en-us">
  <title>
    <?PI_start author="joepublic" comment="Comment #1" ?>Discovering
      <?PI_end?>XML
  </title>
  <related-stuff>
    <?PI_start author="johndoe" comment="Comment #3" ?>
      <a href="otherdoc.xml" />
      <?PI_end?>
  </related-stuff>
</material>

And I would like to rename the processing instruction from 'PI' to 'otherPI', as well as rename the attribute "author" to "user".

The result would look like this:

<?xml version="1.0" encoding="utf-8"?>
<material xml:lang="en-us">
  <title>
    <?otherPI_start user="joepublic" comment="Comment #1"?>Discovering
    <?otherPI_end?>XML
  </title>
  <related-stuff>
    <?otherPI_start user="johndoe" comment="Comment #3"?>
    <a href="otherdoc.xml" />
    <?otherPI_end?>
  </related-stuff>
</material>

Can you help me identify the matching statement in the xsl that would do this?

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
  <xsl:output method="xml" indent="yes" />
  <xsl:template match="node()|@*">
    <xsl:copy>
      <xsl:apply-templates select="node()|@*" />
    </xsl:copy>
  </xsl:template>
  <xsl:template match="processing-instruction('PI_start')">
      <xsl:copy>
        <!-- What should I put here??? -->
      </xsl:copy>
  </xsl:template>
  <xsl:template match="processing-instruction('PI_end')">
      <xsl:copy>
        <!-- What should I put there??? -->
      </xsl:copy>
  </xsl:template>
</xsl:stylesheet>

Solution

To rename a processing instruction, you would do:

<xsl:template match="processing-instruction('PI_start')">
    <xsl:processing-instruction  name="otherPI_start">
        <xsl:value-of select="." />
    </xsl:processing-instruction>
</xsl:template>

If you also want to modify the content, e.g. change author="joepublic" to user="joepublic", you will have to do this using string manipulation - for example:

<xsl:template match="processing-instruction('PI_start')">
    <xsl:processing-instruction  name="otherPI_start">
        <xsl:value-of select="substring-before(., 'author=')" />
        <xsl:text>user=</xsl:text>
        <xsl:value-of select="substring-after(., 'author=')" />
    </xsl:processing-instruction>
</xsl:template>