An xsl:sort element may appear as a child of xsl:for-each-group, and defines how the groups are sorted.

It's not clear what happens if the first such xsl:sort specifies stable="no". Section 14.3 (Grouping) says "If two groups have the same values for all their sort key components, they are processed in order of first appearance." But section 13 (Sorting) suggests that this is not guaranteed in the case where stable="no" is specified.

Proposed resolution: stable="no" should mean what it says, and 14.3 should change to say "If two groups have the same values for all their sort key components, they are processed in order of first appearance if the sort is *stable* [link to termdef] or in an implementation-dependent order otherwise."