XSL: Avoid exporting namespace definitions to resulting XML documents

You can use the exclude-result-prefixes attribute of the xsl:stylesheet element to avoid emitting namespace prefixes into the output document:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
         xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
         xmlns:prefix1="http://www.something.com"
         exclude-result-prefixes="prefix1">

</xsl:stylesheet>

To suppress multiple namespaces from the output document specify them separated by whitespace:

exclude-result-prefixes="prefix1 prefix2 prefix3"

From the XSLT specification:

When a stylesheet uses a namespace declaration only for the purposes of addressing the source tree, specifying the prefix in the exclude-result-prefixes attribute will avoid superfluous namespace declarations in the result tree.