Updating Attribute Values

I'd like to change the values of attribute "href", whenever it appears
inside a "dao" element. From what I can tell, my template is correct,
however when ever I stick anything inside xsl:attribute (replace <!--
do stuff here -->, nothing happens during the transformation. Am I
missing something?

    <xsl:template match="@href[parent::dao]">
        <xsl:attribute name="href">
            <!-- do stuff here -->
        </xsl:attribute>
    </xsl:template>

I'm using XSLT 2.0, Saxon 6.5.5.

Thanks,
Nathan