Lavoisier

<!-- select VO 'dteam' -->
<select nodes="/root/site/vo[@name='dteam']"/>

<!-- select all VOs, grouped by site and VO -->
<select nodes="/root/site/vo">
    <group context="/root/site" by="vo/@name"/>
</select>

<!-- select all VOs, grouped by VO -->
<select nodes="/root/site/vo">
    <group context="/root" by="site/vo/@name"/>
</select>

<!-- select all sites, grouped by VO -->
<select nodes="/root/site">
    <group context="/root" by="site/vo/@name"/>
</select>

<!-- select all sites that support VO 'dteam' (easy version) -->
<select nodes="/root/site[vo/@name='dteam']"/>

<!-- select all sites that support VO 'dteam' (optimized version) -->
<select nodes="/root/site">
    <if-descendant prefix="" name="vo" predicate="@name='dteam'"/>
</select>

<!-- select all sites, grouped by VO name -->
<select nodes="/root/site">
    <group by="vo/@name" sort="" descending=""/>
</select>

<!-- select all VOs, grouped by VO name -->
<select nodes="/root/site/vo">
    <group by="@name" sort="" descending=""/>
</select>

<!-- select all VOs, grouped by site and VO name (with @context-depth) -->
<select nodes="/root/site/vo">
    <group by="@name" sort="" descending="" context-depth="2"/>
</select>

<!-- select all VOs, grouped by site and VO name (without @context-depth) -->
<for nodes="/root/site">
    <connector type="XMLConnector">
        <parameter name="content" eval="current()"/>
    </connector>
    <processors>
        <select nodes="/site/vo">
            <group by="@name" sort="" descending=""/>
        </select>
    </processors>
</for>
<remove nodes="/root/site/vo"/>