<xsl:template match="o:*" />
It strips out all the elements that are defined in the namespace referenced by alias o.
ExplanationA normal template expression has a format similar to the one of below:
<xsl:apply-templates select="author" />
This example processes all the author children of the author-group. By default, the XSLT processor processes each matched element only once. After an author-group element is selected, the processor outputs the author children of the matched element to XML. So, if the xsl:apply-templates element is omitted, the children of the source element are skipped during the transformation.