The optional use-attribute-sets attribute is a white-space-delimited list of one or more qnames of attribute sets. In other words, it is a collection of attribute set names. Each of the xsl:attribute elements in all of the attribute sets are applied to the output in the order in which they occur in the use-attribute-sets attribute. This is done by adding the use-attribute-sets attribute to the HTML tag or XSLT element using the following syntax.