[xsl] xsl:sort on fn:collection() ?

Hi,

Is it possible to sort a collection based on filename?

For example:

<xsl:apply-templates select="collection($model-path)" mode="model">
  <xsl:sort/>
</xsl:apply-templates>

By default, it does not seem to apply in file system order. If I use
xsl:sort, what would I sort on?

thanks,
-Rob