Attributes can also be created by xsl:attribute.

They must be created before children are added to the element.

You can use them on literal elements:

<section>
<xsl:attribute name="id">sect1</xsl:attribute>
</section>

Or on xsl:element constructions

<xsl:element name="section">
<xsl:attribute name="id">sect1</xsl:attribute>
</xsl:element>

The children of xsl:attribute must be text nodes that represent the value of the attribute.

You can use expressions in the name:

<xsl:attribute name="{child/@ref}"/>