On Fri, May 22, 2026 at 11:36:44AM +0000, Susanne Wunsch susanne.wunsch@xxxxxxxxxxxxx scripsit:
> Hi all,
[snip]
> Is there an XSLT 2.0 way that produces identical output but avoids the
> apparent n^2 cost of the sibling-axis idioms above?

https://www.saxonica.com/html/documentation12/xsl-elements/for-each-group.htmlhttps://www.saxonica.com/html/documentation12/xsl-elements/for-each-group.html would be worth a look.

Something vaguely like 

<xsl:for-each-group select="*" group-starting-with="fired-rule">
    <xsl:choose>
        <xsl:when test="current-group()[1] instance of
        element(fired-rule)">
            <xsl:element name="fired-rule">
                <xsl:apply-templates select="head(current-group())/@*"/>
                <xsl:apply-templates select="head(current-group())/node()"/>
                <xsl:apply-templates select="tail(current-group())"/>
            </xsl:element>
         </xsl:when>
         <xsl:otherwise>
            <xsl:apply-templates select="current-group()"/>
         </xsl:otherwise>
     </xsl:choose>
</xsl:for-each-group>

(This is entirely untested.)

Is the pattern; group starting with fired-rule, replicate that fired
rule and put everything after it in the group into it. The same sort of
pattern will work for active-pattern but it'll need to be a distinct
pass in another mode.

Hope that helps!

-- Graydon

--  
Graydon Saunders  | graydonish@xxxxxxxxxxxx
\xDE\xE6s ofer\xE9ode, \xF0isses sw\xE1 m\xE6g.
-- Deor  ("That passed, so may this.")