XSL file to limit hosts and ports only to those that are responsive/open in NMap XML documents

nmap_open_only.xsl

<!--

Quick and dirty XSL file to lessen the size of large NMap
XML files. Below is an example using the lxml library in Python.
Observed to reduce size of a 300MB XML IP protocol scan to 19MB
in less than a minute.

from lxml import etree as ET
document = ET.parse('to_transform.xml')
xslt = ET.parse('nmap_open_only.xsl')
transform = ET.XSLT(xslt)
with open('transformed.xml', 'wb+') as outfile:
    outfile.write(
        ET.tostring(transform(document), pretty_print=True))

-->

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

    <xsl:template match="/">
        <xsl:copy>
            <xsl:apply-templates/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="/nmaprun">
        <nmaprun>
            <xsl:copy-of select="@*|b/@*"/>
            <xsl:copy-of select="/nmaprun/scaninfo"/>
            <xsl:copy-of select="/nmaprun/taskbegin"/>
            <xsl:copy-of select="/nmaprun/taskend"/>
            <xsl:if test="/nmaprun/taskbegin[@task='Ping Scan']">
                <xsl:for-each select="//host/status[@state='up']">
                    <xsl:copy-of select=".."/>
                </xsl:for-each>
            </xsl:if>
            <xsl:if test="/nmaprun/taskbegin[@task!='Ping Scan']">
                <xsl:for-each select="//host">
                    <xsl:choose>
                    <xsl:when test="./ports/port/state[@state='open']">
                        <xsl:copy select=".">
                            <xsl:copy-of select="@*"/>
                            <xsl:copy-of select="./status"/>
                            <xsl:copy-of select="./address"/>
                            <xsl:copy-of select="./hostnames"/>
                            <xsl:copy-of select="./times"/>
                            <xsl:for-each select="./ports/port/state[@state='open']">
                                <ports>
                                    <xsl:copy-of select="../../extraports"/>
                                    <xsl:for-each select="..">
                                        <xsl:copy-of select="."/>
                                    </xsl:for-each>
                                </ports>
                            </xsl:for-each>
                        </xsl:copy>
                    </xsl:when>
                    <xsl:when test=".//hostname">
                        <xsl:copy select="../..">
                            <xsl:copy-of select="@*"/>
                            <!-- Set to up to ensure that hostnames are captured -->
                            <status state="up" reason="user-set" reason_ttl="0"/>
                            <xsl:copy-of select="./address"/>
                            <xsl:copy-of select="./hostnames"/>
                            <xsl:copy-of select="./times"/>
                            <ports/>
                        </xsl:copy>
                    </xsl:when>
                </xsl:choose>
                </xsl:for-each>
            </xsl:if>
        </nmaprun>
    </xsl:template>

</xsl:stylesheet>